USE flag index

---

Global USE flags

Flag	Description
3dfx	Enable support for Voodoo chipsets, also called as 3DFX and TDFX
X	Add support for X11
Xaw3d	Add support for the 3d athena widget set
a52	Enable support for decoding ATSC A/52 streams used in DVD
aac	Enable support for MPEG-4 AAC Audio
aalib	Add support for media-libs/aalib (ASCII-Graphics Library)
accessibility	Add support for accessibility (eg 'at-spi' library)
acl	Add support for Access Control Lists
acpi	Add support for Advanced Configuration and Power Interface
adns	Add support for asynchronous DNS resolution
afs	Add OpenAFS support (distributed file system)
aim	Enable AIM IM protocol support
alsa	Add support for media-libs/alsa-lib (Advanced Linux Sound Architecture)
altivec	Add support for optimizations for G4 and G5/ppc970 processors
ao	Use libao audio output library for sound playback
apache2	Add Apache2 support
apm	Add APM (Advanced Power Management) support
aqua	Include support for the Mac OS X Aqua (Carbon/Cocoa) GUI
atm	Enable Asynchronous Transfer Mode protocol support
audiofile	Add support for libaudiofile where applicable
audit	Enable support for Linux audit subsystem using sys-process/audit
avahi	Add avahi/Zeroconf support
ayatana	Build in support for Ayatana notification using the libindicate or libappindicator plugin
bash-completion	Enable bash-completion support
bcmath	Add support for libbcmath
berkdb	Add support for sys-libs/db (Berkeley DB for MySQL)
bidi	Enable bidirectional language support
big-endian	Big-endian toolchain support
bindist	Flag to enable or disable options for prebuilt (GRP) packages (eg. due to licensing issues)
blas	Add support for the virtual/blas numerical library
bluetooth	Enable Bluetooth Support
bootstrap	!!internal use only!! DO NOT SET THIS FLAG YOURSELF!, used during original system bootstrapping [make stage2]
boundschecking	Add the bounds checking patch by Haj Ten Brugge, this will DISABLE the hardened PIE+SSP patches
branding	Enable Gentoo specific branding
bsf	Enable support for Apache Bean Scripting Framework (dev-java/bsf)
build	!!internal use only!! DO NOT SET THIS FLAG YOURSELF!, used for creating build images and the first half of bootstrapping [make stage1]
bzip2	Use the bzlib compression library
cairo	Enable support for the cairo graphics library
calendar	Add support for calendars (not using mcal!)
canna	Add support for the Canna kana to kanji conversion engine
caps	Use Linux capabilities library to control privilege
cdb	Add support for the CDB database engine from the author of qmail
cdda	Add Compact Disk Digital Audio (Standard Audio CD) support
cddb	Access cddb servers to retrieve and submit information about compact disks
cdinstall	Copy files from the CD rather than asking the user to copy them, mostly used with games
cdparanoia	Enable cdparanoia (audio CD ripper) support
cdr	Add support for CD writer hardware
cgi	Add CGI script support
cjk	Add support for Multi-byte character languages (Chinese, Japanese, Korean)
clamav	Add support for Clam AntiVirus software (usually with a plugin)
connman	Add support for net-misc/connman
coreaudio	Build the CoreAudio driver on Mac OS X systems
cracklib	Support for cracklib strong password checking
crypt	Add support for encryption -- using mcrypt or gpg where applicable
cscope	Enable cscope interface -- in vim for example
css	Enable reading of encrypted DVDs
ctype	Enable ctype functions
cups	Add support for CUPS (Common Unix Printing System)
curl	Add support for client-side URL transfer library
custom-cflags	Build with user-specified CFLAGS (unsupported)
cvs	Enable CVS (Concurrent Versions System) integration
cxx	Build support for C++ (bindings, extra libraries, code generation, ...)
dbi	Enable dev-db/libdbi (database-independent abstraction layer) support
dbm	Add support for generic DBM databases
dbus	Enable dbus support for anything that needs it (gpsd, gnomemeeting, etc)
debug	Enable extra debug codepaths, like asserts and extra output. If you want to get meaningful backtraces see https://wiki.gentoo.org/wiki/Project:Quality_Assurance/Backtraces
dedicated	Add support for dedicated game servers (some packages do not provide clients and servers at the same time)
dga	Add DGA (Direct Graphic Access) support for X
directfb	Add support for DirectFB layer (library for FB devices)
djvu	Support DjVu, a PDF-like document format esp. suited for scanned documents
doc	Add extra documentation (API, Javadoc, etc). It is recommended to enable per package instead of globally
dri	Enable direct rendering: used for accelerated 3D and some 2D, like DMA
dts	Enable DTS Coherent Acoustics decoder support
dv	Enable support for a codec used by many camcorders
dvb	Add support for DVB (Digital Video Broadcasting)
dvd	Add support for DVDs
dvdr	Add support for DVD writer hardware (e.g. in xcdroast)
eds	Enable support for Evolution-Data-Server (EDS)
emacs	Add support for GNU Emacs
emboss	Add support for the European Molecular Biology Open Software Suite
encode	Add support for encoding of audio or video files
enscript	Add enscript support to colourize code stored in the repository
evo	Add support for mail-client/evolution
examples	Install examples, usually source code
exif	Add support for reading EXIF headers from JPEG and TIFF images
expat	Enable the use of dev-libs/expat for XML parsing
fam	Enable FAM (File Alteration Monitor) support
fastcgi	Add support for the FastCGI interface
fbcon	Add framebuffer support for the console, via the kernel
ffmpeg	Enable ffmpeg/libav-based audio/video codec support
fftw	Use FFTW library for computing Fourier transforms
filecaps	Use Linux file capabilities to control privilege rather than set*id (this is orthogonal to USE=caps which uses capabilities at runtime e.g. libcap)
firebird	Add support for the Firebird relational database
flac	Add support for FLAC: Free Lossless Audio Codec
flatfile	Add dbm support for flat files
fltk	Add support for the Fast Light Toolkit gui interface
fontconfig	Support for configuring and customizing font access via media-libs/fontconfig
foomaticdb	Add support for the foomatic printing driver database
fortran	Add support for fortran
freetds	Add support for the TDS protocol to connect to MSSQL/Sybase databases
freewnn	Add support for FreeWnn kana to kanji conversion engine
ftp	Add FTP (File Transfer Protocol) support
gcj	Enable building with gcj (The GNU Compiler for the Javatm Programming Language)
gd	Add support for media-libs/gd (to generate graphics on the fly)
gdbm	Add support for sys-libs/gdbm (GNU database libraries)
geoip	Add geoip support for country and city lookup based on IPs
geolocation	Enable physical position determination
ggi	Add support for media-libs/libggi (non-X video api/drivers)
gif	Add GIF image support
gimp	Build a plugin for the GIMP
git	Enable git (version control system) support
glut	Build an OpenGL plugin using the GLUT library
gmp	Add support for dev-libs/gmp (GNU MP library)
gnome	Add GNOME support
gnome-keyring	Enable support for storing passwords via gnome-keyring
gnuplot	Enable support for gnuplot (data and function plotting)
gnutls	Add support for net-libs/gnutls (TLS 1.0 and SSL 3.0 support)
gphoto2	Add digital camera support
gpm	Add support for sys-libs/gpm (Console-based mouse driver)
gps	Add support for Global Positioning System
graphicsmagick	Build and link against GraphicsMagick instead of ImageMagick (might require USE=imagemagick if optional)
graphviz	Add support for the Graphviz library
gsl	Use the GNU scientific library for calculations
gsm	Add support for the gsm lossy speech compression codec
gstreamer	Add support for media-libs/gstreamer (Streaming media)
gtk	Add support for x11-libs/gtk+ (The GIMP Toolkit)
guile	Add support for the guile Scheme interpreter
gzip	Compress files with Lempel-Ziv coding (LZ77)
handbook	Enable handbooks generation for packages by KDE
hardened	Activate default security enhancements for toolchain (gcc, glibc, binutils)
hddtemp	Enable monitoring of hdd temperature (app-admin/hddtemp)
hdf5	Add support for the Hierarchical Data Format v5
hscolour	Include coloured haskell sources to generated documentation (dev-haskell/hscolour)
ibm	Add support for IBM ppc64 specific systems
iconv	Enable support for the iconv character set conversion library
icq	Enable ICQ IM protocol support
icu	Enable ICU (Internationalization Components for Unicode) support, using dev-libs/icu
idn	Enable support for Internationalized Domain Names
ieee1394	Enable FireWire/iLink IEEE1394 support (dv, camera, ...)
imagemagick	Enable optional support for the ImageMagick or GraphicsMagick image converter
imap	Add support for IMAP (Internet Mail Application Protocol)
imlib	Add support for imlib, an image loading and rendering library
infiniband	Enable Infiniband RDMA transport support
inifile	Add dbm support for .ini files
inotify	Enable inotify filesystem monitoring support
introspection	Add support for GObject based introspection
iodbc	Add support for iODBC library
ios	Enable support for Apple's iDevice with iOS operating system (iPad, iPhone, iPod, etc)
ipod	Enable support for iPod device access
ipv6	Add support for IP version 6
iwmmxt	Add support for optimizations for ARM iwMMXt instructions
jack	Add support for the JACK Audio Connection Kit
java	Add support for Java
javascript	Enable javascript support
jbig	Enable jbig-kit support for tiff, Hylafax, ImageMagick, etc
jingle	Enable voice calls for jabber
jit	Enable just-in-time compilation for improved performance. May prevent use of some PaX memory protection features in Gentoo Hardened.
joystick	Add support for joysticks in all packages
jpeg	Add JPEG image support
jpeg2k	Support for JPEG 2000, a wavelet-based image compression format
kde	Add support for KDE (K Desktop Environment)
kerberos	Add kerberos support
ladspa	Enable the ability to support ladspa plugins
lame	Prefer using LAME libraries for MP3 encoding support
lapack	Add support for the virtual/lapack numerical library
lash	Add LASH Audio Session Handler support
latex	Add support for LaTeX (typesetting package)
lcms	Add lcms support (color management engine)
ldap	Add LDAP support (Lightweight Directory Access Protocol)
libass	SRT/SSA/ASS (SubRip / SubStation Alpha) subtitle support
libav	Prefer libav over ffmpeg whenever both are supported
libcaca	Add support for colored ASCII-art graphics
libedit	Use the libedit library (replacement for readline)
libffi	Enable support for Foreign Function Interface library
libnotify	Enable desktop notification support
libressl	Use dev-libs/libressl as SSL provider (might need ssl USE flag), packages should not depend on this USE flag
libsamplerate	Build with support for converting sample rates using libsamplerate
libwww	Add libwww support (General purpose WEB API)
lirc	Add support for lirc (Linux's Infra-Red Remote Control)
livecd	!!internal use only!! DO NOT SET THIS FLAG YOURSELF!, used during livecd building
lm_sensors	Add linux lm_sensors (hardware sensors) support
lua	Enable Lua scripting support
lzma	Support for LZMA (de)compression algorithm
lzo	Enable support for lzo compression
m17n-lib	Enable m17n-lib support
mad	Add support for mad (high-quality mp3 decoder library and cli frontend)
maildir	Add support for maildir (~/.maildir) style mail spools
matroska	Add support for the matroska container format (extensions .mkv, .mka and .mks)
mbox	Add support for mbox (/var/spool/mail) style mail spools
memcached	Add support for memcached
memlimit	Add memory usage limiting in supporting programs
mhash	Add support for the mhash library
migemo	Enable migemo support for Japanese
mikmod	Add libmikmod support to allow playing of SoundTracker-style music files
milter	Add sendmail mail filter (milter) support
mime	Add MIME support
minimal	Install a very minimal build (disables, for example, plugins, fonts, most drivers, non-critical features)
mmap	Add mmap (memory map) support
mms	Support for Microsoft Media Server (MMS) streams
mng	Add support for libmng (MNG images)
modplug	Add libmodplug support for playing SoundTracker-style music files
modules	Build the kernel modules
mono	Build Mono bindings to support dotnet type stuff
motif	Add support for the Motif toolkit
mozilla	Add support for the Mozilla web-browser
mp3	Add support for reading mp3 files
mp4	Support for MP4 container format
mpeg	Add libmpeg3 support to various packages
mpi	Add MPI (Message Passing Interface) layer to the apps that support it
mplayer	Enable mplayer support for playback or encoding
msn	Enable MSN Messenger IM protocol support
mssql	Add support for Microsoft SQL Server database
mtp	Enable support for Media Transfer Protocol
mule	Add multi-language support to XEmacs
multilib	On 64bit systems, if you want to be able to compile 32bit and 64bit binaries
musepack	Enable support for the musepack audio codec
musicbrainz	Lookup audio metadata using MusicBrainz community service (musicbrainz.org)
mysql	Add mySQL Database support
mysqli	Add support for the improved mySQL libraries
nas	Add support for network audio sound
ncurses	Add ncurses support (console display library)
neXt	Enable neXt toolkit
neon	Enable optimization support for ARM NEON processors
netboot	Enable network booting
netcdf	Enable NetCDF data format support
networkmanager	Enable net-misc/networkmanager support
nis	Support for NIS/YP services
nls	Add Native Language Support (using gettext - GNU locale utilities)
nntp	Add support for newsgroups (Network News Transfer Protocol)
nocd	Install all files required to run the application without a CD mounted
nptl	Enable support for Native POSIX Threads Library, the new threading module (requires linux-2.6 or better usually)
nsplugin	Build plugin for browsers supporting the Netscape plugin architecture (that is almost any modern browser)
ocaml	Add support/bindings for the Ocaml language
ocamlopt	Enable ocamlopt support (ocaml native code compiler) -- Produces faster programs (Warning: you have to disable/enable it at a global scale)
oci8	Add Oracle 8 Database Support
oci8-instant-client	Use dev-db/oracle-instantclient-basic as Oracle provider instead of requiring a full Oracle server install
odbc	Add ODBC Support (Open DataBase Connectivity)
offensive	Enable potentially offensive items in packages
ofx	Enable support for importing (and exporting) OFX (Open Financial eXchange) data files
ogg	Add support for the Ogg container format (commonly used by Vorbis, Theora and flac)
openal	Add support for the Open Audio Library
openexr	Support for the OpenEXR graphics file format
opengl	Add support for OpenGL (3D graphics)
openmp	Build support for the OpenMP (support parallel computing), requires >=sys-devel/gcc-4.2 built with USE="openmp"
oracle	Enable Oracle Database support
orc	Use dev-lang/orc for just-in-time optimization of array operations
osc	Enable support for Open Sound Control
oscar	Enable Oscar (AIM/ICQ) IM protocol support
oss	Add support for OSS (Open Sound System)
pam	Add support for PAM (Pluggable Authentication Modules) - DANGEROUS to arbitrarily flip
pch	Enable precompiled header support for faster compilation at the expense of disk space and memory (>=sys-devel/gcc-3.4 only)
pcmcia	Add support for PCMCIA slots/devices found on laptop computers
pcntl	Add support for process creation functions
pcre	Add support for Perl Compatible Regular Expressions
pda	Add support for portable devices
pdf	Add general support for PDF (Portable Document Format), this replaces the pdflib and cpdflib flags
perl	Add optional support/bindings for the Perl language
php	Include support for the PHP language
pie	Build programs as Position Independent Executables (a security hardening technique)
plasma	Build optional KDE plasma addons
plotutils	Add support for plotutils (library for 2-D vector graphics)
png	Add support for libpng (PNG images)
policykit	Enable PolicyKit authentication support
portaudio	Add support for the crossplatform portaudio audio API
posix	Add support for POSIX-compatible functions
postgres	Add support for the postgresql database
postscript	Enable support for the PostScript language (often with ghostscript-gpl or libspectre)
ppds	Add support for automatically generated ppd (printing driver) files
prefix	Defines if a Gentoo Prefix offset installation is used
prelude	Add support/bindings for the Prelude Intrusion Detection System
profile	Add support for software performance analysis (will likely vary from ebuild to ebuild)
pulseaudio	Add support for PulseAudio sound server
python	Add optional support/bindings for the Python language
qdbm	Add support for the qdbm (Quick Database Manager) library
qmail-spp	Add support for qmail SMTP plugins
qt4	Add support for the Qt GUI/Application Toolkit version 4.x
qt5	Add support for the Qt 5 application and UI framework
quicktime	Add support for OpenQuickTime
radius	Add support for RADIUS authentication
raw	Add support for raw image formats
rdp	Enables RDP/Remote Desktop support
readline	Enable support for libreadline, a GNU line-editing library that almost everyone wants
recode	Enable support for the GNU recode library
rss	Enable support for RSS feeds
ruby	Add support/bindings for the Ruby language
samba	Add support for SAMBA (Windows File and Printer sharing)
sasl	Add support for the Simple Authentication and Security Layer
savedconfig	Use this to restore your config from /etc/portage/savedconfig ${CATEGORY}/${PN}. Make sure your USE flags allow for appropriate dependencies
scanner	Add support for scanner hardware (e.g. build the sane frontend in kdegraphics)
sctp	Support for Stream Control Transmission Protocol
sdl	Add support for Simple Direct Layer (media library)
seamonkey	Add support for the Seamonkey web-browser
seccomp	Enable seccomp (secure computing mode) to perform system call filtering at runtime to increase security of programs
selinux	!!internal use only!! Security Enhanced Linux support, this must be set by the selinux profile or breakage will occur
semantic-desktop	Cross-KDE support for semantic search and information retrieval
session	Add persistent session support
sharedmem	Add support for shared memory use
shorten	Add support for the shorten audio compressor
simplexml	Support for SimpleXML
skey	Enable S/Key (Single use password) authentication support
slang	Add support for the slang text display library (it's like ncurses, but different)
slp	Add Service Locator Protocol support
smartcard	Enable smartcard support
smp	Enable support for multiprocessors or multicore systems
sndfile	Add support for libsndfile
snmp	Add support for the Simple Network Management Protocol if available
soap	Add support for SOAP (Simple Object Access Protocol)
sockets	Add support for tcp/ip sockets
socks5	Add support for the socks5 proxy
sound	Enable sound support
source	Zip the sources and install them
sox	Add support for Sound eXchange (SoX)
speex	Add support for the speex audio codec (used for speech)
spell	Add dictionary support
sqlite	Add support for sqlite - embedded sql database
ssl	Add support for Secure Socket Layer connections
startup-notification	Enable application startup event feedback mechanism
static	!!do not set this during bootstrap!! Causes binaries to be statically linked instead of dynamically
static-libs	Build static versions of dynamic libraries as well
subversion	Enable subversion (version control system) support
suid	Enable setuid root program, with potential security risks
svg	Add support for SVG (Scalable Vector Graphics)
svga	Add support for SVGAlib (graphics library)
sybase	Add support for the Sybase SQL Database Server
sybase-ct	Add support for Sybase-CT
symlink	Force kernel ebuilds to automatically update the /usr/src/linux symlink
syslog	Enable support for syslog
systemd	Enable use of systemd-specific libraries and features like socket activation or session tracking
sysvipc	Support for System V-compatible inter-process communication
szip	Use the szip compression library
taglib	Enable tagging support with taglib
tcl	Add support the Tcl language
tcmalloc	Use the dev-util/google-perftools libraries to replace the malloc() implementation with a possibly faster one
tcpd	Add support for TCP wrappers
test	Workaround to pull in packages needed to run with FEATURES=test. Portage-2.1.2 handles this internally, so don't set it in make.conf/package.use anymore
theora	Add support for the Theora Video Compression Codec
threads	Add threads support for various packages. Usually pthreads
tidy	Add support for HTML Tidy
tiff	Add support for the TIFF image format
timidity	Build with Timidity++ (MIDI sequencer) support
tk	Add support for Tk GUI toolkit
tokenizer	Add support for the PHP file parser
truetype	Add support for FreeType and/or FreeType2 fonts
uclibc	Enable uclibc specific patches and build or link uclibc
udev	Enable virtual/udev integration (device discovery, power and storage device support, etc)
udisks	Enable storage management support (automounting, volume monitoring, etc)
unicode	Add support for Unicode
unwind	Add support for call stack unwinding and function name resolution
upnp	Enable UPnP port mapping support
upnp-av	Enable UPnP audio/video streaming support
upower	Enable power management support
usb	Add USB support to applications that have optional USB support (e.g. cups)
v4l	Enable support for video4linux (using linux-headers or userspace libv4l libraries)
vaapi	Enable Video Acceleration API for hardware decoding
vala	Enable bindings for dev-lang/vala
vanilla	Do not add extra patches which change default behaviour; DO NOT USE THIS ON A GLOBAL SCALE as the severity of the meaning changes drastically
vcd	Video CD support
vdpau	Enable the Video Decode and Presentation API for Unix acceleration interface
vhosts	Add support for installing web-based applications into a virtual-hosting environment
videos	Install optional video files (used in some games)
vim-syntax	Pulls in related vim syntax scripts
vnc	Enable VNC (remote desktop viewer) support
vorbis	Add support for the OggVorbis audio codec
wavpack	Add support for wavpack audio compression tools
wayland	Enable dev-libs/wayland backend
wddx	Add support for Web Distributed Data eXchange
webkit	Add support for the WebKit HTML rendering/layout engine
webp	Add support for the WebP image format
wifi	Enable wireless network functions
wmf	Add support for the Windows Metafile vector image format
wxwidgets	Add support for wxWidgets/wxGTK GUI toolkit
x264	Enable h264 encoding using x264
xattr	Add support for extended attributes (filesystem-stored metadata)
xcb	Support the X C-language Binding, a replacement for Xlib
xcomposite	Enable support for the Xorg composite extension
xemacs	Add support for XEmacs
xface	Add xface support used to allow a small image of xface format to be included in an email via the header 'X-Face'
xft	Build with support for XFT font renderer (x11-libs/libXft)
xine	Add support for the XINE movie libraries
xinerama	Add support for the xinerama X11 extension, which is mandatory if you work in multiple monitors setup
xinetd	Add support for the xinetd super-server
xml	Add support for XML files
xmlrpc	Support for xml-rpc library
xmp	Enable support for Extensible Metadata Platform (Adobe XMP)
xmpp	Enable support for Extensible Messaging and Presence Protocol (XMPP) formerly known as Jabber
xosd	Sends display using the X On Screen Display library
xpm	Add support for XPM graphics format
xscreensaver	Add support for XScreenSaver extension
xv	Add in optional support for the Xvideo extension (an X API for video playback)
xvid	Add support for xvid.org's open-source mpeg-4 codec
yahoo	Enable Yahoo Messenger IM protocol support
yaz	Add in optional support for the Z39.50 Protocol for Information Retrieval (YAZ)
zeroconf	Support for DNS Service Discovery (DNS-SD)
zlib	Add support for zlib (de)compression
zsh-completion	Enable zsh completion support

Local USE flags

app-accessibility

brltty

api	build brltty's application program interface
beeper	support the console tone generator
contracted-braille	support in-line contracted braille
fm	support for the sound card synthesizer
midi	support the musical instrument digital interface
pcm	support for sound card digital audio
speech	speech support

eflite

16k_voice	Use a higher-quality voice.

emacspeak

espeak	Adds support for the espeak tts engine

festival-it

mbrola	Adds support for mbrola voices

freetts

jsapi	build Java Speech API (JSAPI)
mbrola	Adds support for mbrola voices

orca

braille	Enable braille support

simon

opencv	Use media-libs/opencv
pim	Enable support for KDE PIM resources integration
sphinx	Build sphinx backend (pulls app-accessibility/julius if disabled

speech-dispatcher

espeak	Adds support for espeak speech engine
flite	Adds support for flite speech engine

speechd-el

brltty	brltty support

app-admin

bcfg2

cheetah	Include dev-python/cheetah support
genshi	Include dev-python/genshi support
server	Installs scripts to be used on the server-side of this app

calamares

pythonqt	Enable PythonQt-based module interface

clsync

cgroups	Use cgroups to limit /dev access.
cluster	Enable clustering support (allows master-master clsync on multiple hosts). Not fully implemented yet.
control-socket	Enable AF_UNIX control socket support.
extra-debug	Enable extra debugging. This will hurt performance badly. Be ready for tons of output.
extra-hardened	Enable extra security checks. This will hurt performance.
gio	Enable GIO for FS monitoring (glib based alternative to inotify interface, not recommended; if both are compiled, may be selected at runtime).
highload-locks	Allows to use spinlocks for short delays instead of mutexes, but only on SMP systems.
namespaces	Enable namespaces isolation.

collectd

contrib	Install user-contributed files in the doc directory
filecaps	When set collectd daemon will have set required capabilities to run most plugins even if run as unprivileged user
java	Must be set (workaround for java-pkg-opt-2 eclass limitation) when you want java or genericjmx plugin
udev	Enable optional udev usage in disk plugin; Required for smart plugin
xfs	Enable optional capability to filter on XFS file system in df plugin; Requires XFS headers from sys-fs/xfsprogs

conky

apcupsd	Enable support for sys-power/apcupsd
audacious	Enable monitoring of music played by media-sound/audacious
cmus	Enable monitoring of music played by media-sound/cmus
eve	Enable support for the eve-online skill monitor
ical	Enable support for events from iCalendar (RFC 5545) files using dev-libs/libical
iostats	Enable support for per-task I/O statistics
irc	Enable support for displaying everything from an irc channel using net-libs/libircclient
lua-cairo	Enable if you want Lua Cairo bindings
lua-imlib	Enable if you want Lua Imlib2 bindings
lua-rsvg	Enable if you want Lua RSVG bindings
math	Enable support for glibc's libm math library
moc	Enable monitoring of music played by media-sound/moc
mpd	Enable monitoring of music controlled by media-sound/mpd
nano-syntax	Enable syntax highlighting for app-editors/nano
nvidia	Enable reading of nvidia card temperature sensors via media-video/nvidia-settings
portmon	Enable support for tcp (ip4) port monitoring
thinkpad	Enable support for IBM/Lenovo notebooks
weather-metar	Enable support for metar weather service
weather-xoap	Enable support for metar and xoap weather service
webserver	Enable support to act as a webserver serving conkys output using net-libs/libmicrohttpd
xmms2	Enable monitoring of music played by media-sound/xmms2

diamond

mongo	Enable MongoDB support
redis	Enable Redis support

diradm

automount	Support for automount data in LDAP
irixpasswd	Support for storing separate IRIX passwords

elektra

augeas	Enable plugin for reading and writing configuration files with help from Augeas
ini	Enable new, advanced ini support
simpleini	Enable simpleini support
uname	Enable uname information for the key database
yajl	Enable yajl support

gkrellm

X	Build both the X11 gui (gkrellm) and the server (gkrellmd). Disabling this flag builds the server only
gnutls	Enable SSL support for mail checking with net-libs/gnutls (overrides 'ssl' USE flag)
hddtemp	Enable monitoring harddrive temperatures via app-admin/hddtemp
lm_sensors	Enable monitoring sensors via sys-apps/lm_sensors
ntlm	Enable NTLM authentication for mail checking with net-libs/libntlm
ssl	Enable SSL support for mail checking with dev-libs/openssl

glance

swift	Adds swift storage support

gtkdiskfree

gtk2	Support GTK+ 2.x instead of GTK+ 3.x

hddtemp

network-cron	Monthly cronjob to update hddtemp.db.

keepass

aot	Generate native code at build time, rather than runtime.

keepassxc

autotype	Add support to autotype the passwords into other applications
http	Add http support
yubikey	Enable database unlocking via YubiKey.

lastpass-cli

X	Use x11-misc/xclip or x11-misc/xsel to copy passwords to the clipboard.
pinentry	Use app-crypt/pinentry to prompt for passwords.

logrotate

acl	Installs acl support
cron	Installs cron file
selinux	Installs Security Enhanced Linux support

matter

entropy	Add Entropy support

mcollective

client	Install client utilities

mms-agent

monitoring	Install the monitoring agent

openrc-settingsd

systemd	Use the versions of dbus and polkit files provided by sys-apps/systemd

packagekit-base

command-not-found	Enable packagekit support on shell "command not found"
cron	Install cron script for auto-update
elogind	Enable elogind support to get user session
entropy	Enable Entropy backend

pass

X	Use x11-misc/xclip to copy passwords to the clipboard.
dmenu	Add support for x11-misc/dmenu with the 'passmenu' program.
fish-completion	Enable fish completion support.
git	Use dev-vcs/git for password revisions.
importers	Allow importing passwords from other password managers using various contributed scripts.

passwordsafe

minimal	Avoid collision with app-misc/pwsafe
xml	Enable XML import support
yubikey	Enable support for Yubikey

prelude-manager

dbx	Enables Prelude Manager storing Prelude alerts into database through dev-libs/libpreludedb .
tcpwrapper	Enables Prelude Manager using tcp wrapper. It requires sys-apps/tcp-wrappers .

puppet

augeas	Enable augeas support
diff	Enable diff support
experimental	Add patches for things in testing
rrdtool	Enable rrdtool support
shadow	Enable shadow support

puppet-agent

experimental	Add patches for things in testing
puppetdb	Adds puppetdb support

puppetserver

puppetdb	Adds support for connecting to puppetdb

pwgen

livecd	Install init script for root password scrambling on boot

rsyslog

dbi	Build the general database output module (requires dev-db/libdbi)
elasticsearch	Build the Elasticsearch output module (requires net-misc/curl)
gcrypt	Add support for encrypted log files using dev-libs/libgcrypt
grok	Build the grok modify module (requires dev-libs/grok)
jemalloc	Use dev-libs/jemalloc for allocations.
kafka	Build the Apache Kafka input/output module (requires dev-libs/librdkafka)
kerberos	Build the GSSAPI input and output module (requires virtual/krb5)
libressl	Use dev-libs/libressl for building the rfc5424hmac modify module (requires rfc5424hmac USE flag)
mdblookup	Build the MaxMind DB lookup message modify plugin using dev-libs/libmaxminddb
mongodb	Build the MongoDB output module (requires dev-libs/libmongo-client)
mysql	Build the MySQL database output module (requires virtual/mysql)
normalize	Build the normalize modify module (requires dev-libs/libee and dev-libs/liblognorm)
omhttpfs	Build the httpfs output module (requires net-misc/curl)
omudpspoof	Build the udpspoof output module (requires net-libs/libnet)
postgres	Build the PostgreSQL database output module (requires dev-db/postgresql)
rabbitmq	Build the RabbitMQ output module (requires net-libs/rabbitmq-c)
redis	Build the Redis output module using (requires dev-libs/hiredis)
relp	Build the Reliable Event Logging Protocol (RELP) output module (requires dev-libs/librelp)
rfc3195	Build the rfc3195 input module (requires dev-libs/liblogging)
rfc5424hmac	Build the rfc5424hmac modify module (requires dev-libs/openssl or dev-libs/libressl)
snmp	Build the snmp modify and output module (requires net-analyzer/net-snmp)
ssl	Add support for encrypted client/server communication (requires net-libs/gnutls)
systemd	Build the journal input and output module (requires sys-apps/systemd)
usertools	Installs the user tools (rsgtutil, rscryutil...) corresponding to the set USE flags
uuid	Include UUIDs in messages (requires sys-apps/util-linux)
zeromq	Build the ZeroMQ input and output modules (requires net-libs/czmq)

sagan

libdnet	Add support for dev-libs/libdnet
lognorm	Add support for log/rules normalizations via dev-libs/liblognorm
pcap	Add support for network packet capture via net-libs/libpcap
smtp	Build witch SMTP (E-Mail) support
snort	Add support to interact with Snort IDE using net-analyzer/snortsam'

sagan-rules

lognorm	Install normalize rules support with dev-libs/liblognorm

salt

cherrypy	Enable support for using cherrypy.
gnupg	Enable support for gnupg via python-gnupg.
keyring	Enable support for keyrings via python-keyring.
libcloud	Enable salt-cloud support via libcloud.
libvirt	Support managing virtual machines with app-emulation/libvirt.
mako	Add support for using the mako template engine for parsing salt states.
mongodb	Support returning data to a mongodb server.
neutron	Support the OpenStack neutron network service.
nova	Enable support for the OpenStack Nova API
openssl	Add support for using TLS via OpenSSL.
portage	Add support for package state enforcement using sys-apps/portage
raet	Add support for the new RAET transport.
redis	Support returning data to a redis database.
timelib	Use timelib to parse english textual date descriptions.
zeromq	Add support for the zeromq transport.

sshguard

ipfilter	Enable ipfilter firewall support (only for *bsd)

sudo

gcrypt	Use SHA2 from dev-libs/libgcrypt instead of sudo's internal SHA2
offensive	Let sudo print insults when the user types the wrong password
openssl	Use SHA2 from dev-libs/openssl instead of sudo's internal SHA2
sendmail	Allow sudo to send emails with sendmail

sysklogd

logrotate	use app-admin/logrotate for rotating logs rather than custom cron scripts

syslog-ng

amqp	Enable support for AMQP destinations
http	Enable support for HTTP destinations
json	Enable support for JSON template formatting via dev-libs/json-c
mongodb	Enable support for mongodb destinations
pacct	Enable support for reading Process Accounting files (EXPERIMENTAL, Linux only)
redis	Enable support for Redis destinations
smtp	Enable support for SMTP destinations
spoof-source	Enable support for spoofed source addresses

sysstat

isag	Install isag, the Interactive System Activity Graph tool

systemrescuecd-x86

isohybrid	Pass downloaded images through isohybrid in order to make it possible to copy them directly to USB media and boot (requires sys-boot/syslinux at build time).

testdisk

ewf	Include ewf library
ntfs	Include the ability to read NTFS filesystems
reiserfs	Include reiserfs reading ability

tripwire

ssl	Adds support for Secure Socket Layer connections
static	Builds the package statically
tools	Installs app-admin/mktwpol, providing scripts for the installation/setup of tripwire, including generating the tripwire policy file and maintenance of the tripwire database

ulogd

json	Build JSON output plugin to save packets in JSON file format
nfacct	Build NFACCT input plugin to support traffic accounting via nfnetlink_acct
nfct	Build NFCT input plugin to support stateful flow-based logging via nfnetlink_conntrack
nflog	Build NFLOG input plugin to support stateless packet-based logging via nfnetlink_log
pcap	Build PCAP output plugin to save packets in libpcap file format
ulog	Build ULOG input plugin to support deprecated packet-based logging via ULOG target

webalizer

xtended	Include the 404 extension

webapp-config

portage	Propagete python_targets dependencies to sys-apps/portage

yaala

storable	Support for persistence of Perl data structures.

app-antivirus

clamav

clamdtop	A Top like tool which shows what clamd is currently scanning amongst other things
metadata-analysis-api	Enables collection of file property metadata using ClamAV API for analysis by ClamAV bytecode programs.

app-arch

cabextract

extras	Install experimental extra tools: wince_info and wince_rename for examining and processing Windows CE installation cabinet header files; cabinfo for examining the structure of a cab file.

cfv

bittorrent	Enable support for checking .torrent files

deltarpm

system-zlib	Use system sys-libs/zlib. Do not enable features of rsync friendly.

dpkg

update-alternatives	Install update-alternatives

dump

ermt	encrypted rmt support
uuid	Enable UUID support

engrampa

caja	Enable engrampa to integrate with mate-base/caja by providing entries in its context menu
gtk3	Build with GTK+3 instead of GTK+2
magic	Enable filetype auto-detection via sys-apps/file
packagekit	Enable support for installing via app-admin/packagekit based on archive type

file-roller

nautilus	Build contextual menu extension for gnome-base/nautilus.
packagekit	Enable support for the distro-neutral package manager GUI app-admin/packagekit

gzip

pic	disable optimized assembly code that is not PIC friendly

innoextract

c++0x	Compile innoextract using the C++11 standard
debug	Enable debug logging and the --debug command-line option
lzma	Enable support for extracting lzma-compressed installers using app-arch/xz-utils

libarchive

bzip2	Allow accessing bzip2-compressed archives through libbz2 (which comes with app-arch/bzip2). This only affects libarchive's native support: bsdtar will keep using bunzip2 as a filter if that's not built-in.
e2fsprogs	Use file flags from sys-fs/e2fsprogs headers instead of virtual/os-headers headers
lz4	Enable support for LZ4 compression using app-arch/lz4
nettle	Use dev-libs/nettle as crypto backend
zlib	Allow accessing gzip-compressed archives through sys-libs/zlib. This only affects libarchive's native support: bsdtar will keep using gunzip as a filter if that's not built-in. It's also needed for supporting extraction of ZIP files.

lz4

valgrind	Enable usage of dev-util/valgrind in tests

p7zip

rar	Enable support for non-free rar decoder

pbzip2

symlink	Install symlinks which override app-arch/bzip2 implementation

pigz

symlink	Install symlinks which override app-arch/gzip implementation

rar

all_sfx	Install all SFX (Self-Extracting) files rather than just the native format (allows creation of Windows EXEs on Linux ELF systems)

tar

minimal	just install `tar`

unzip

natspec	Use dev-libs/libnatspec to correctly decode non-ascii file names archived in Windows.

xz-utils

extra-filters	Build additional filters that are not used in any of the default xz presets. This includes delta and BCJ coders, additional match finders and SHA256 checks.

zip

natspec	Use dev-libs/libnatspec to correctly decode non-ascii file names archived in Windows.

app-backup

amanda

ndmp	Support for the NDMP protocol
s3	Support for backing up to the Amazon S3 system
xfs	Support for backing up raw XFS filesystems using xfsdump

backup-manager

s3	Support for backing up to the Amazon S3 system

bacula

bacula-clientonly	Disable DB support, and just build a client
bacula-nodir	Disable building of director
bacula-nosd	Disable building of storage daemon
logwatch	Install support files for logwatch

bareos

cephfs	Enable cephfs storage backend
clientonly	Only install file-daemon (client)
director	Install director
fastlz	Enable support vor lz4, lz4hc and lzfast using dev-libs/bareos-fastlzlib
glusterfs	Enable glusterfs storage backend
gnutls	When ssl is enabled, use GnuTLS instead of OpenSSL
jansson	JSON API support using JANSSON for director
lmdb	enable build of LMDB support for faster accurate backup
logwatch	Install support files for logwatch
ndmp	Enable support for NDMP (Network Data Management Protocol)
rados	Enable rados storage backend
rados-striper	Enable use of rados-striper
scsi-crypto	Enable low level SCSI crypto support
sql-pooling	Enable SQL pooling support
storage-daemon	Install storage daemon (bareos-sd)

btrbk

pv	Use sys-apps/pv to enable progress bar functionality

bup

web	Support browsing backups via a web interface

dar

dar32	Enables --enable-mode=32 option, which replace infinite by 32 bit integers
dar64	Enables --enable-mode=64 option, which replace infinite by 64 bit integers
gcrypt	Enables strong encryption support
gpg	Enables usage of asymetric crypto algorithms

deja-dup

nautilus	Build gnome-base/nautilus extension

duplicity

s3	Support for backing up to the Amazon S3 system

holland-backup-mysql-meta

lvm	Install Holland LVM Plugin
mysqldump	Install Holland mysqldump Plugin
mysqlhotcopy	Install Holland mysqlhotcopy Plugin

rear

udev	Have ReaR start backup when attaching your USB drive.

snapper

btrfs	Include Btrfs support sys-fs/btrfs-progs
ext4	Include Ext4 support sys-fs/e2fsprogs
lvm	Enable LVM thinprovisioned snapshots support sys-fs/lvm2
xattr	Add support for getting and setting POSIX extended attributes, through sys-apps/attr.

tsm

tsm_cit	IBM Tivoli Common Inventory Technology
tsm_hw	Difference snapshot support for NetApp and N-Series file servers

zbackup

tartool	Install tartool utility

app-benchmarks

filebench

auto-completion	Enable command-line autocompletion using dev-libs/libtecla

httperf

idleconn	Build with the idleconn program

ramspeed

pic	Force shared libraries to be built as PIC (this is slower)

sysbench

aio	Enable libaio support

app-cdr

brasero

libburn	Enable dev-libs/libburn backend
nautilus	Build the gnome-base/nautilus extension
packagekit	Enable support for the distro-neutral package manager GUI app-admin/packagekit
playlist	Enable support for playlists through dev-libs/totem-pl-parser
tracker	Enable audio playlist search using the app-misc/tracker indexer

cdemu

cdemu-daemon	Pull app-cdr/cdemu-daemon dependency, useful in chroot environment (bug #315491). Do not disable until you know what you are doing.

cdrdao

gcdmaster	Enable building of gcdmaster application

cuetools

extras	Install additional script that tag files based on cue/toc file information

dvdisaster

debug	Enable memory debugging.

gaffitter

scripts	Install additional gaffitter scripts for external programs

mirage2iso

pinentry	Support app-crypt/pinentry password input backend.

app-crypt

aespipe

asm	Enable assembly modules
cpu_flags_x86_padlock	Use VIA padlock instructions, detected at run time, code still works on non-padlock processors

ccid

kobil-midentity	Build and install Kobil_mIDentity_switch tool
twinserial	Enable twinserial reader

codecrypt

cryptopp	Build algorithms that need Crypto++ support dev-libs/crypto++

eid-mw

dialogs	Enable "askaccess" dialog box, by using x11-libs/gtk+
gtk	All dialogs are available, by using x11-libs/gtk+
p11-kit	Support for app-crypt/p11-kit.
xpi	Build and install an extension for Mozilla browsers.

ekeyd

minimal	Only install the ekey-egd-linux service rather than the full ekeyd package.
munin	Install a plugin for net-analyzer/munin to graph statistical data from ekeyd.
usb	Build the libusb-based userland daemon for accessing the EntropyKey (alternative to the CDC USB driver). It is suggested to use this option by default, as the CDC driver in the kernel often seems to be fragile (or the gadget implementation on the EntropyKey is too buggy), and can cause various problems.

gnupg

mta	Build mta support using virtual/mta.
smartcard	Build scdaemon software. Enables usage of OpenPGP cards. For other type of smartcards, try app-crypt/gnupg-pkcs11-scd. Bring in dev-libs/libusb as a dependency; enable scdaemon.
tofu	Enable support for Trust on First use trust model; requires dev-db/sqlite.
tools	Install extra tools (including gpgsplit and gpg-zip).
usb	Build direct CCID access for scdaemon; requires dev-libs/libusb.
wks-server	Install the wks-server

gnupg-pkcs11-scd

proxy	Build the gnupg-pkcs11-scd-prox

gpgme

common-lisp	Install common-lisp files

heimdal

hdb-ldap	Adds support for LDAP as a database backend
otp	Adds support for one-time passwords
pkinit	Adds support for PKINIT for the initial ticket

hmaccalc

fips	Enable NSS FIPS mode and support only the FIPS-compliant functions

johntheripper

cuda	Use nvidia cuda toolkit for speeding up cracking on capable devices
mozilla	Support mozilla password cracking
opencl	Enable opencl support for speeding up cracking on capable devices

kbfs

git	Build the Git remote helper for storing repositories in Keybase

kstart

afs	Enables afs support which means you can acquire an afs token and set PAGs. It's recommended to set this USE if you need authenticated access to an AFS cell for your daemon/app.

libb2

native-cflags	Use CFLAGS as determined by configure script. These flags will enable all CPU specific features it find available, to further optimise the implementation. This discards any existing CFLAGS set in make.conf or similar.

libu2f-host

systemd	Use user ACLs rather than plugdev group to give user access to the HIDRAW device.

mit-krb5

doc	Creates and installs the API and implementation documentation. This is only useful if you want to develop software which depends on kerberos.
keyutils	Enable for the keyring ccache using keyutils.
openldap	Enable support for ldap as a database backend.
pkinit	Enable pkinit support for the initial ticket.

ophcrack

tables	Require the additional tables used to carry out cracking (app-crypt/ophcrack-tables)

ophcrack-tables

vistafree	Installs the free Vista ophcrack tables
xpfast	Installs the fast XP ophcrack tables
xpsmall	Installs the small free XP ophcrack tables

p11-kit

asn1	Enable ASN.1 certificate support
trust	Build the trust policy module

qca

botan	Enable botan plugin
gcrypt	Enable gcrypt plugin
gpg	Enable GnuPG plugin
logger	Enable logger plugin
nss	Enable NSS plugin
pkcs11	Enable PKCS#11 plugin
sasl	Enable SASL plugin
softstore	Enable softstore plugin

rhash

openssl	Add support for hashes from dev-libs/openssl

seahorse

ldap	Enable seahorse to manipulate GPG keys on a LDAP server.

tpm-tools

pkcs11	Build Token data management utilities based on OpenCryptoki's (dev-libs/opencryptoki) PKCS#11 implementation.

veracrypt

asm	Enable assembly for optimization

zulucrypt

gnome	Enable support for the freedesktop.org Secret Service API via app-crypt/libsecret
kwallet	Enable encrypted storage of passwords with kde-frameworks/kwallet
udev	Whether udev will be consulted when deciding if a volume is system or not

app-dicts

aspell-be

classic	Support classic spelling by default

gwaei

hunspell	Enable app-text/hunspell spellchecking and morphological analysis
mecab	Enable app-text/mecab support

myspell-pt

preao	Use the pre ortographic agreement version of the dictionary

app-doc

clsync-docs

api	Install doxygen generated API docs.

csound-manual

html	Install HTML documentation

doxygen

clang	support for sys-devel/clang assisted parsing
dot	allow to create dot graphs using media-gfx/graphviz
doxysearch	build doxyindexer and doxysearch.cgi

kicad-doc

html	Generate documentation in HTML format
pdf	Generate documentation in PDF format

linuxfromscratch

htmlsingle	Install all-on-one-page HTML version.

pms

binary	Download pre-built files instead of building from sources
html	Generate PMS as .html as well
twoside	Enable two-sided layout suitable for printing

root-docs

api	Generate html API documentation
http	Build HttpServer documentation
math	Provide all math related documentation
metric	Default to A4 paper size and metric measurement. Letter will be used otherwise

tldp-howto

html	Install multi-chapter HTML docs
htmlsingle	Install all-on-one-page HTML docs
pdf	Install pdf docs
text	Install plain-text docs

app-editors

bluefish

gtk2	Enable GTK2 instead of GTK3 even if GTK3 is available
gtk3	Enable GTK3 interface (default)
gucharmap	Enable gucharmap dictionary plugin
python	Enable Python integration for zen-coding plugin
spell	Enable spell checking capabilities via enchant library

emacs

athena	Enable the MIT Athena widget set (x11-libs/libXaw)
dynamic-loading	Enable loading of dynamic libraries at runtime
games	Support shared score files for games
gconf	Use gnome-base/gconf to read the system font name
gfile	Use gfile (dev-libs/glib) for file notification
gsettings	Use gsettings (dev-libs/glib) to read the system font name
gtk3	Prefer version 3 of the GIMP Toolkit to version 2 (x11-libs/gtk+)
gzip-el	Compress bundled Emacs Lisp source
hesiod	Enable support for net-dns/hesiod
imagemagick	Use media-gfx/imagemagick for image processing
libxml2	Use dev-libs/libxml2 to parse XML instead of the internal Lisp implementations
pax_kernel	Enable building under a PaX enabled kernel
source	Install C source files and make them available for find-function
toolkit-scroll-bars	Use the selected toolkit's scrollbars in preference to Emacs' own scrollbars
wide-int	Prefer wide Emacs integers (typically 62-bit). This option has an effect only on architectures where "long" and "long long" types have different size.
xwidgets	Enable use of GTK widgets in Emacs buffers (requires GTK3)

emacs-vcs

athena	Enable the MIT Athena widget set (x11-libs/libXaw)
dynamic-loading	Enable loading of dynamic libraries at runtime
games	Support shared score files for games
gconf	Use gnome-base/gconf to read the system font name
gfile	Use gfile (dev-libs/glib) for file notification
gsettings	Use gsettings (dev-libs/glib) to read the system font name
gtk3	Prefer version 3 of the GIMP Toolkit to version 2 (x11-libs/gtk+)
gzip-el	Compress bundled Emacs Lisp source
hesiod	Enable support for net-dns/hesiod
imagemagick	Use media-gfx/imagemagick for image processing
libxml2	Use dev-libs/libxml2 to parse XML instead of the internal Lisp implementations
mailutils	Retrieve e-mail using net-mail/mailutils instead of the internal movemail substitute
pax_kernel	Enable building under a PaX enabled kernel
source	Install C source files and make them available for find-function
threads	Add elisp threading support
toolkit-scroll-bars	Use the selected toolkit's scrollbars in preference to Emacs' own scrollbars
wide-int	Prefer wide Emacs integers (typically 62-bit). This option has an effect only on architectures where "long" and "long long" types have different size.
xwidgets	Enable use of GTK widgets in Emacs buffers (requires GTK3)

fe

sendmail	Send mail after editor abend

gedit-plugins

charmap	Insert special characters just by clicking on them
git	Shows document changes related to git's HEAD
terminal	Embed a terminal in the bottom pane
zeitgeist	Build the plugin to inject events to gnome-extra/zeitgeist

gvim

gtk3	Enable GTK+3 interface
luajit	Use dev-lang/luajit instead of dev-lang/lua
netbeans	Include netbeans external editor integration support
racket	Enable support for Scheme using dev-scheme/racket

jasspa-microemacs

nanoemacs	Build NanoEmacs instead of MicroEmacs

joe

xterm	Enable full xterm clipboard support

latexila

latexmk	Install dev-tex/latexmk (used by default for the build tools)
rubber	Install dev-tex/rubber (can be used for the build tools)

leafpad

emacs	Enable Emacs key theme

mousepad

gtk3	Use GTK+3 instead of GTK+2

nano

debug	Enable debug messages and assert warnings. Note that these will all be sent straight to stderr rather than some logging facility.
justify	Enable justify/unjustify functions for text formatting.
magic	Add magic file support (sys-apps/file) to automatically detect appropriate syntax highlighting
minimal	Disable all fancy features, including ones that otherwise have a dedicated USE flag (such as spelling).

ne

tinfo	Link against libtinfo from sys-libs/ncurses

neovim

clipboard	Enable clipboard support through a provider
jemalloc	Use dev-libs/jemalloc for allocations
luajit	Use dev-lang/luajit instead of dev-lang/lua
nvimpager	Install nvimpager symlink to less.sh macro
tui	Build the neovim unix tui

pluma

gtk3	Build with GTK+3 instead of GTK+2

qhexedit2

gui	Install Qt5 hex editor

tea

aspell	Enable spellchecking using app-text/aspell
hunspell	Enable spellchecking using app-text/hunspell
qml	Enable support for plugins using QML

vim

X	Link console vim against X11 libraries to enable title and clipboard features in xterm
luajit	Use dev-lang/luajit instead of dev-lang/lua
racket	Enable support for Scheme using dev-scheme/racket
terminal	Enable terminal emulation support
vim-pager	Install vimpager and vimmanpager links

vis

tre	more memory efficient regex search using dev-libs/tre

xemacs

athena	Chooses the MIT Athena widget set
dnd	Enables support for the x11-libs/dnd drag-n-drop library
eolconv	Support detection and translation of newline conventions
pop	Support POP for mail retrieval
xim	Enable X11 XiM input method

zile

valgrind	Enable usage of dev-util/valgrind in tests

app-emacs

anything

extensions	Install optional extensions

auctex

preview-latex	Use bundled preview-latex

bbdb

tex	Install plain TeX support files
vm	Add support for app-emacs/vm

calfw

howm	Add support for the app-emacs/howm note-taking tool

company-mode

ropemacs	Install backend for dev-python/ropemacs

emacs-common-gentoo

games	Support shared score files for games

emhacks

jde	Enable support for Java Development Environment

org-mode

contrib	Install user-contributed files
odt-schema	Install non-free schema files for OpenDocument Text exporter

remember

bbdb	Include support for app-emacs/bbdb
planner	Include support for app-emacs/planner

slime

xref	Install xref.lisp cross-referencing tool

vm

bbdb	Include support for app-emacs/bbdb

wanderlust

bbdb	Include support for app-emacs/bbdb

wikipedia-mode

outline-magic	Enable support for outline-mode extensions (app-emacs/outline-magic)

app-emulation

bochs

3dnow	Enable support for emulating 3DNow! instructions (incomplete)
avx	Enable support for emulating Advanced Vector Extensions (AVX)
debugger	Enable debugger (slows down emulation)
gdb	Enable support for the remote GDB stub
x86-64	Enable support for emulation of 64-bit CPUs

containerd

btrfs	Support for BTRFS snapshot driver

crossover-bin

capi	Enable ISDN support via CAPI

docker

apparmor	Enable AppArmor support.
aufs	Enables dependencies for the "aufs" graph driver, including necessary kernel flags.
btrfs	Enables dependencies for the "btrfs" graph driver, including necessary kernel flags.
container-init	Makes the a staticly-linked init system tini available inside a container.
device-mapper	Enables dependencies for the "devicemapper" graph driver, including necessary kernel flags.
overlay	Enables dependencies for the "overlay" graph driver, including necessary kernel flags.
pkcs11	Enables pkcs-11 support.

docker-runc

ambient	Enable support for ambient capability
apparmor	Enable AppArmor support

dosemu

fluidsynth	use media-sound/fluidsynth for MIDI emulation

e-uae

capslib	Add CAPS library support
sdl-sound	Use media-libs/sdl-sound for audio output

free42

alsa	Adds support for Advanced Linux Sound Architecture

fuse-utils

gcrypt	Use dev-libs/libgcrypt for low-level crypto of some features, including logfiles.

ganeti

drbd	Enable DRBD support
experimental	Enable experimental patches. Warning! This will break RPC within major versions if the patches applied differ!
haskell-daemons	Build haskell daemons instead of python
htools	Enable htools support
kvm	Enable KVM support
lxc	Enable Linux Countainers support
monitoring	Enable the ganeti monitoring daemon
multiple-users	Enable support for running VMs as different users
rbd	Enable rados block device support via sys-cluster/ceph
restricted-commands	Enable restricted commands in the node daemon
xen	Enable Xen support

hyperd

libvirt	Enable support for KVM via libvirt
xen	Enable support for the Xen Hypervisor

libguestfs

erlang	Build Erlang bindings
fuse	Enable image mount support via fuse
inspect-icons	Use media-gfx/icoutilsfor acces icon file in image and inspect it
systemtap	Use dev-util/systemtap to inspect VM via "probes" way

libspectrum

gcrypt	Use dev-libs/libgcrypt for low-level crypto of some features, including logfiles.

libvirt

apparmor	Enable AppArmor support
firewalld	DBus interface to iptables/ebtables allowing for better runtime management of your firewall.
fuse	Allow LXC to use sys-fs/fuse for mount points
glusterfs	Enable GlusterFS support via sys-cluster/glusterfs
iscsi	Allow using an iSCSI remote storage server as pool for disk image storage
libssh	Use net-libs/libssh to communicate with remote libvirtd hosts, for example: qemu+libssh://server/system
libvirtd	Builds the libvirtd daemon as well as the client utilities instead of just the client utilities
lvm	Allow using the Logical Volume Manager (sys-fs/lvm2) as pool for disk image storage
lxc	Support management of Linux Containers virtualisation (app-emulation/lxc)
macvtap	Support for MAC-based TAP (macvlan/macvtap). For networking instead of the normal TUN/TAP. It has its advantages and disadvantages. macvtap support requires very new kernels and is currently evolving. Support for this is experimental at best.
nfs	Allow using Network File System mounts as pool for disk image storage
numa	Use NUMA for memory segmenting via sys-process/numactl and sys-process/numad
openvz	Support management of OpenVZ virtualisation (openvz-sources)
parted	Allow using real disk partitions as pool for disk image storage, using sys-block/parted to create, resize and delete them.
pcap	Support auto learning IP addreses for routing
phyp	Support IBM HMC / IVM hypervisor via PHYP protocol
qemu	Support management of QEMU virtualisation (app-emulation/qemu)
rbd	Enable rados block device support via sys-cluster/ceph
uml	Support management of User Mode Linux virtualisation
vepa	Virtual Ethernet Port Aggregator (VEPA) / 802.1Qbg support. Relies on macvtap support.
virt-network	Enable virtual networking (NAT) support for guests. Includes all the dependencies for NATed network mode. Effectively any network setup that relies on libvirt to setup and configure network interfaces on your host. This can include bridged and routed networks ONLY if you are allowing libvirt to create and manage the underlying devices for you. In some cases this requires enabling the 'netcf' USE flag (currently unavailable).
virtualbox	Support management of VirtualBox virtualisation (one of app-emulation/virtualbox or app-emulation/virtualbox-bin)
wireshark-plugins	Build the net-analyzer/wireshark plugin for the Libvirt RPC protocol
xen	Support management of Xen virtualisation (app-emulation/xen)
zfs	Enable ZFS backend storage sys-fs/zfs

lxc

cgmanager	Enable support for cgroup management using app-admin/cgmanager

lxd

daemon	Build the system daemon, not just the client tool
dnsmasq	Depend on dnsmasq to provide DHCP and DNS.

open-vm-tools

doc	Generate API documentation
grabbitmqproxy	Enable grabbitmqproxy
pic	Force shared libraries to be built as PIC
vgauth	Enable vgauth

playonlinux

winbind	Enables support for the winbind auth daemon

q4wine

ico	Enable ico support via media-gfx/icoutils
iso	Support unprivileged mounting of ISO9660 images via sys-fs/fuseiso
wineappdb	Enable Wine AppDB browser support

qemu

accessibility	Adds support for braille displays using brltty
aio	Enables support for Linux's Async IO
alsa	Enable alsa output for sound emulation
curl	Support ISOs / -cdrom directives vis HTTP or HTTPS.
fdt	Enables firmware device tree support
glusterfs	Enables GlusterFS cluster fileystem via sys-cluster/glusterfs
gnutls	Enable TLS support for the VNC console server. For 1.4 and newer this also enables WebSocket support. For 2.0 through 2.3 also enables disk quorum support.
gtk2	Use gtk-2 instead of gtk-3
iscsi	Enable direct iSCSI support via net-libs/libiscsi instead of indirectly via the Linux block layer that sys-block/open-iscsi does.
jpeg	Enable jpeg image support for the VNC console server
ncurses	Enable the ncurses-based console
nfs	Enable NFS support
numa	Enable NUMA support
pin-upstream-blobs	Pin the versions of BIOS firmware to the version included in the upstream release. This is needed to sanely support migration/suspend/resume/snapshotting/etc... of instances. When the blobs are different, random corruption/bugs/crashes/etc... may be observed.
png	Enable png image support for the VNC console server
pulseaudio	Enable pulseaudio output for sound emulation
rbd	Enable rados block device backend support, see http://ceph.newdream.net/wiki/QEMU-RBD
sdl	Enable the SDL-based console
sdl2	Use libsdl2 instead of libsdl
snappy	Enable support for snappy compression
spice	Enable Spice protocol support via app-emulation/spice
ssh	Enable SSH based block device support via net-libs/libssh2
static	Build the User and Software MMU (system) targets as well as tools as static binaries
static-user	Build the User targets as static binaries
systemtap	Enable SystemTAP/DTrace tracing
tci	Enable the TCG Interpreter which can speed up or slowdown workloads depending on the host and guest CPUs being emulated. In the future it will be a runtime option but for now its compile time.
usb	Enable USB passthrough via dev-libs/libusb
usbredir	Use sys-apps/usbredir to redirect USB devices to another machine over TCP
vde	Enable VDE-based networking
vhost-net	Enable accelerated networking using vhost-net, see http://www.linux-kvm.org/page/VhostNet
virgl	Enable experimental Virgil 3d (virtual software GPU)
virtfs	Enable VirtFS via virtio-9p-pci / fsdev. See http://wiki.qemu.org/Documentation/9psetup
vte	Enable terminal support (x11-libs/vte) in the GTK+ interface
xattr	Add support for getting and setting POSIX extended attributes, through sys-apps/attr. Requisite for the virtfs backend.
xen	Enables support for Xen backends
xfs	Support xfsctl() notification and syncing for XFS backed virtual disks.

qt-virt-manager

smartcard	Enable smartcard remoting using app-emulation/libcacard

rkt

actool	Install the actool for ACI manipulation
rkt_stage1_coreos	Download and use a prebuilt stage1.aci from CoreOS
rkt_stage1_fly	Build stage1-fly.aci
rkt_stage1_host	Assemble stage1.aci from host binaries
rkt_stage1_kvm	This flag has been replaced by the rkt_stage1_kvm_* flags
rkt_stage1_kvm_lkvm	Build stage1-kvm-lkvm.aci
rkt_stage1_kvm_qemu	Build stage1-kvm-qemu.aci
rkt_stage1_src	Build the stage1.aci from source

runc

ambient	Enable support for ambient capabilities set (Requires Linux kernel 4.3 or later).
apparmor	Enable AppArmor support.

runv

libvirt	Enable support for KVM via libvirt
xen	Enable support for the Xen Hypervisor

spice

lz4	Enable support for LZ4 compression using app-arch/lz4
smartcard	Enable smartcard remoting using app-emulation/libcacard

spice-vdagent

consolekit	Use sys-auth/consolekit to determine the master vdagentd in case of multiple running vdagentds (highly recommended)

uae

scsi	Enable the uaescsi.device

vagrant

virtualbox	Use VirtualBox provider.

vice

ethernet	Enable ethernet emulation
fullscreen	Enable the ability to run fullscreen
sdlsound	Use media-libs/libsdl for sound support
vte	Enable support for x11-libs/vte in the GTK+ interface

virt-manager

policykit	Enables sys-auth/polkit authentication support, required when using app-emulation/libvirt with PolicyKit authentication
sasl	Depend on the proper libraries needed to connect to SASL-enabled libvirtd instances (e.g. Kerberos-protected instances).

virt-viewer

spice	Support connecting to SPICE-enabled virtual machines.
vnc	Support connecting to VNC-enabled virtual machines.

virt-what

dmi	Use sys-apps/dmidecode to read firmware data

virtualbox

headless	Build without any graphic frontend
lvm	Build VBoxVolInfo that needs devicemapper from sys-fs/lvm2.
pax_kernel	Apply patch needed for pax enabled kernels.
sdk	Enable building of SDK
udev	Controls installation of special USB udev rules.
vboxwebsrv	Build and install the VirtualBox webservice

virtualbox-bin

additions	Install Guest System Tools ISO
chm	Install kchmviewer binary to enable online help (in MS CHM format)
headless	Install without any graphic frontend
rdesktop-vrdp	Install the rdesktop client integration
sdk	Enable building of SDK
vboxwebsrv	Install the VirtualBox webservice

virtualbox-modules

pax_kernel	Apply patch needed for pax enabled kernels

vov

gprof	build with profiling support

wine

capi	Enable ISDN support via CAPI
custom-cflags	Bypass strip-flags; use at your own peril
d3d9	Apply highly experimental patches for Gallium Nine support. This patch may break some applications.
dos	Pull in games-emulation/dosbox to run DOS applications
gecko	Add support for the Gecko engine when using iexplore
gstreamer	Use media-libs/gstreamer to provide DirectShow functionality;
mono	Add support for .NET using Wine's Mono add-on
netapi	Use libnetapi from net-fs/samba to support Windows networks in netapi32.dll
opencl	Enable OpenCL support
osmesa	Add support for OpenGL in bitmaps using libOSMesa
pcap	Support packet capture software (e.g. wireshark)
perl	Install helpers written in perl (winedump/winemaker)
pipelight	Apply Wine-Staging patches for Pipelight/Silverlight support
prelink	Run prelink on DLLs during build; For versions before wine-1.7.55 or hardened, do not disable if you do not know what this means as it can break things at runtime
realtime	Pull in sys-auth/rtkit for low-latency pulseaudio support
run-exes	Use Wine to open and run .EXE and .MSI files
s3tc	Pull in media-libs/libtxc_dxtn for DXTn texture compression, needed for many games
samba	Add support for NTLM auth. see http://wiki.winehq.org/NtlmAuthSetupGuide and http://wiki.winehq.org/NtlmSigningAndSealing
staging	Apply Wine-Staging patches for advanced feature support that haven't made it into upstream Wine yet
themes	Support GTK+:3 window theming through Wine-Staging
udev	Use virtual/libudev to provide plug and play support

wine-any

capi	Enable ISDN support via CAPI
custom-cflags	Bypass strip-flags; use at your own peril
d3d9	Apply highly experimental patches for Gallium Nine support. This patch may break some applications.
dos	Pull in games-emulation/dosbox to run DOS applications
gecko	Add support for the Gecko engine when using iexplore
gstreamer	Use media-libs/gstreamer to provide DirectShow functionality;
mono	Add support for .NET using Wine's Mono add-on
netapi	Use libnetapi from net-fs/samba to support Windows networks in netapi32.dll
opencl	Enable OpenCL support
osmesa	Add support for OpenGL in bitmaps using libOSMesa
pcap	Support packet capture software (e.g. wireshark)
perl	Install helpers written in perl (winedump/winemaker)
pipelight	Apply Wine-Staging patches for Pipelight/Silverlight support
prelink	Run prelink on DLLs during build; For versions before wine-1.7.55 or hardened, do not disable if you do not know what this means as it can break things at runtime
realtime	Pull in sys-auth/rtkit for low-latency pulseaudio support
run-exes	Use Wine to open and run .EXE and .MSI files
s3tc	Pull in media-libs/libtxc_dxtn for DXTn texture compression, needed for many games
samba	Add support for NTLM auth. see http://wiki.winehq.org/NtlmAuthSetupGuide and http://wiki.winehq.org/NtlmSigningAndSealing
staging	Apply Wine-Staging patches for advanced feature support that haven't made it into upstream Wine yet
themes	Support GTK+:3 window theming through Wine-Staging
udev	Use virtual/libudev to provide plug and play support

wine-d3d9

capi	Enable ISDN support via CAPI
custom-cflags	Bypass strip-flags; use at your own peril
d3d9	Apply highly experimental patches for Gallium Nine support. This patch may break some applications.
dos	Pull in games-emulation/dosbox to run DOS applications
gecko	Add support for the Gecko engine when using iexplore
gstreamer	Use media-libs/gstreamer to provide DirectShow functionality;
mono	Add support for .NET using Wine's Mono add-on
netapi	Use libnetapi from net-fs/samba to support Windows networks in netapi32.dll
opencl	Enable OpenCL support
osmesa	Add support for OpenGL in bitmaps using libOSMesa
pcap	Support packet capture software (e.g. wireshark)
perl	Install helpers written in perl (winedump/winemaker)
prelink	Run prelink on DLLs during build; For versions before wine-1.7.55 or hardened, do not disable if you do not know what this means as it can break things at runtime
realtime	Pull in sys-auth/rtkit for low-latency pulseaudio support
run-exes	Use Wine to open and run .EXE and .MSI files
samba	Add support for NTLM auth. see http://wiki.winehq.org/NtlmAuthSetupGuide and http://wiki.winehq.org/NtlmSigningAndSealing
udev	Use virtual/libudev to provide plug and play support

wine-staging

capi	Enable ISDN support via CAPI
custom-cflags	Bypass strip-flags; use at your own peril
dos	Pull in games-emulation/dosbox to run DOS applications
gecko	Add support for the Gecko engine when using iexplore
gstreamer	Use media-libs/gstreamer to provide DirectShow functionality;
mono	Add support for .NET using Wine's Mono add-on
netapi	Use libnetapi from net-fs/samba to support Windows networks in netapi32.dll
opencl	Enable OpenCL support
osmesa	Add support for OpenGL in bitmaps using libOSMesa
pcap	Support packet capture software (e.g. wireshark)
perl	Install helpers written in perl (winedump/winemaker)
pipelight	Apply Wine-Staging patches for Pipelight/Silverlight support
prelink	Run prelink on DLLs during build; For versions before wine-1.7.55 or hardened, do not disable if you do not know what this means as it can break things at runtime
realtime	Pull in sys-auth/rtkit for low-latency pulseaudio support
run-exes	Use Wine to open and run .EXE and .MSI files
s3tc	Pull in media-libs/libtxc_dxtn for DXTn texture compression, needed for many games
samba	Add support for NTLM auth. see http://wiki.winehq.org/NtlmAuthSetupGuide and http://wiki.winehq.org/NtlmSigningAndSealing
staging	Apply Wine-Staging patches for advanced feature support that haven't made it into upstream Wine yet
themes	Support GTK+:3 window theming through Wine-Staging
udev	Use virtual/libudev to provide plug and play support

wine-vanilla

capi	Enable ISDN support via CAPI
custom-cflags	Bypass strip-flags; use at your own peril
dos	Pull in games-emulation/dosbox to run DOS applications
gecko	Add support for the Gecko engine when using iexplore
gstreamer	Use media-libs/gstreamer to provide DirectShow functionality;
mono	Add support for .NET using Wine's Mono add-on
netapi	Use libnetapi from net-fs/samba to support Windows networks in netapi32.dll
opencl	Enable OpenCL support
osmesa	Add support for OpenGL in bitmaps using libOSMesa
pcap	Support packet capture software (e.g. wireshark)
perl	Install helpers written in perl (winedump/winemaker)
prelink	Run prelink on DLLs during build; For versions before wine-1.7.55 or hardened, do not disable if you do not know what this means as it can break things at runtime
realtime	Pull in sys-auth/rtkit for low-latency pulseaudio support
run-exes	Use Wine to open and run .EXE and .MSI files
samba	Add support for NTLM auth. see http://wiki.winehq.org/NtlmAuthSetupGuide and http://wiki.winehq.org/NtlmSigningAndSealing
udev	Use virtual/libudev to provide plug and play support

winetricks

rar	Pull in app-arch/unrar for extraction of rar-compressed game files

x48

readline	Enables support for libreadline

xe-guest-utilities

xenstore	Use xenstore binaries bundled by Citrix instead of building app-emulation/xen-tools

xen

efi	Adds efi boot support, requires LDFLAG -melf_x86_64 for amd64
flask	Enable the Flask XSM module from NSA

xen-tools

api	Build the C libxenapi bindings
flask	Enable the Flask XSM module from NSA
hvm	Enable support for hardware based virtualization (VT-x,AMD-v)
ocaml	Enable support for the ocaml language
ovmf	Enable support to boot UEFI guest vm, needed by hvm
pam	Enable pam support
pygrub	Install the pygrub boot loader
qemu	Enable IOEMU support via the use of qemu-dm
qemu-traditional	Build the old qemu traditional device model (useful only if you cannot change to the new device model e.g. Windows VMs)
screen	Enable support for running domain U console in an app-misc/screen session
system-qemu	Using app-emulation/qemu instead of the bundled one
system-seabios	Using sys-firmware/seabios instead of the bundled one

xtrs

ls-dos	Install LS-DOS disk images for Model 4P

app-eselect

eselect-php

fpm	Enable the FastCGI Process Manager SAPI

app-forensics

afflib

fuse	Enable extra fuse thingies
qemu	Enable qemu stuff
s3	Enable support for Amazon S3

aide

e2fs	Enable support for checking file attributes on ext2/ext3/ext4 filesystems
prelink	Bypass prelinking when calculating checksums

chkrootkit

cron	Install cron script for weekly rootkit scans

libewf

bfio	Enables libbfio for chaining file in file handling
ewf	Enables the v1 API
fuse	Enable fuse support for ewfmount
rawio	Enables raw IO handling
uuid	Enable UUID support in the ewftools

openscap

gconf	Build the gconf independant probes
nss	Prefer NSS over libgcrypt as the crypto engine
rpm	Compiles the RPM probes
sce	Enables Script Check Engine (SCE) support
sql	Build the sql independant probes

quickfuzz

archs	support archive formats
codes	support cource code formats
docs	support document formats
imgs	support image formats
media	support media formats
net	support networking formats
pki	support PKI formats

sleuthkit

aff	Enable extra aff formats
ewf	Enable libewf support

app-i18n

anthy

canna-2ch	Enable support for app-dicts/canna-2ch

canna

canuum	Build canuum

fcitx

autostart	Enable XDG-compatible autostart of Fcitx
enchant	Enable Enchant backend (using app-text/enchant) for spelling hinting
gtk2	Install input method module for GTK+ 2
gtk3	Install input method module for GTK+ 3
opencc	Enable OpenCC engine (using app-i18n/opencc) for converter between Simplified Chinese and Traditional Chinese
pango	Enable support for x11-libs/pango
qt4	Install input method module for Qt 4
table	Install table input methods for Simplified Chinese

fcitx-libpinyin

dictionary-manager	Install dictionary manager

fcitx-unikey

macro-editor	Install macro editor

freewnn

uum	Build uum

ibus

emoji	Enable support for Emoji
gconf	Enable support for gnome-base/gconf
gtk2	Enable support for x11-libs/gtk+:2

ibus-chewing

gconf	Enable support for gnome-base/gconf

ibus-handwrite

zinnia	Enable support for app-i18n/zinnia

ibus-libpinyin

boost	Compile against dev-libs/boost libraries
opencc	Enable support for app-i18n/opencc

ibus-m17n

gtk2	Build with x11-libs/gtk+:2 instead of x11-libs/gtk+:3

ibus-pinyin

boost	Enable support for dev-libs/boost

ibus-unikey

gtk2	Enable support for x11-libs/gtk+:2

im-chooser

gtk2	Build with x11-libs/gtk+:2 instead of x11-libs/gtk+:3
xfce	Enable support for XFCE panel

imsettings

gconf	Enable support for gnome-base/gconf
gtk2	Build with x11-libs/gtk+:2 instead of x11-libs/gtk+:3
xfconf	Enable support for xfce-base/xfconf

kimera

anthy	Enable support for app-i18n/anthy

mozc

fcitx4	Enable support for app-i18n/fcitx 4
gui	Install graphical user interface tool (mozc_tool)
handwriting-tegaki	Use handwriting recognition model from app-i18n/tegaki-zinnia-japanese
handwriting-tomoe	Use handwriting recognition model from app-i18n/zinnia-tomoe
ibus	Enable support for app-i18n/ibus
renderer	Enable native candidate window

pyzy

boost	Enable support for dev-libs/boost
doc	Generate API documentation
opencc	Enable support for app-i18n/opencc

scim

gtk3	Enable support for x11-libs/gtk+:3

scim-anthy

gtk3	Enable support for x11-libs/gtk+:3
kasumi	Use Anthy dictionary maintenance tool (app-dicts/kasumi)

tomoe

hyperestraier	Enable support for app-text/hyperestraier

translate-shell

tts	Enable text-to-speech support

uim

anthy	Enable support for app-i18n/anthy input method
eb	Enable support for dev-libs/eb
gtk3	Enable support for x11-libs/gtk+:3
skk	Enable support for app-i18n/skk-jisyo

app-laptop

hdapsd

libconfig	Require dev-libs/libconfig to allow the daemon to read a configuration file at startup

ibam

gkrellm	Enable building of app-admin/gkrellm module

pbbuttonsd

ibam	Enable support for Intelligent Battery Monitoring
macbook	Enable support for the Macbook and Macbook Pro

thinkfan

atasmart	include libatasmart support to get disc temperature

tp_smapi

hdaps	Install a compatible HDAPS module

app-leechcraft

lc-azoth

acetamide	Build Acetamide, the IRC protocol support
adiumstyles	Build support for Adium styles
astrality	Build Astrality, support for protocols provided by Telepathy
autoidler	Build support for automatic status changing according to user idle time
autopaste	Build Autopaste for pasting long texts to pastebins
birthdaynotifier	Build Birthday Notifier for you to not forget about birthdays of your contacts.
chathistory	Build ChatHistory which stories chat history
depester	Build Depester which enables to ignore MUC participants
embedmedia	Build EmbedMedia for embedding flash videos and images directly into chat windows
herbicide	Build Herbicide, a basic antispam plugin
hili	Build HiLi which allows to customize highlight settings in MUCs
isterique	Build Isterique plugin for neutralizing excessive caps lock usage
juick	Build plugin for the Juick.com microblogging service
keeso	Build plugin for changing text into SoMEtHInG lIKe THiS
lastseen	Build plugin for client-side recording of the last online/available time
media	Enable media calls
metacontacts	Build plugin for metacontacts support
murm	Build Murm, the VKontakte messaging support via their native API (instead of XMPP)
nativeemoticons	Build support for native Azoth's emoticons packs
otroid	Build OTRoid, plugin for the Off-the-Record deniable encryption system
sarin	Build Sarin, Tox protocol support module. Please add mva overlay to use net-libs/tox
shx	Build shell command executor plugin
standardstyles	Build support for standard Azoth styles engine
vader	Bulid Vader, the MRIM (Mail.Ru Agent) protocol support plugin
velvetbird	Build support for protocols provided by libpurple
woodpecker	Build Woodpecker, the Twitter client plugin
xtazy	Build Xtazy for publishing currently playing tune

lc-blasq

deathnote	Support LiveJournal FotoBilder service
rappor	Support VKontakte service
spegnersi	Support Flickr service
vangog	Support Picasa service

lc-blogique

hestia	Allows one to keep a local blog
metida	Support for the LiveJournal blogging platform

lc-core

qwt	Support for QML plotting item through x11-libs/qwt

lc-gmailnotifier

notify	Pull in a plugin to show notifications from GMail Notiifer
quark	Pull in a plugin to show GMail Notifier's quark

lc-lmp

fradj	Build FrAdj, the equalizer effect module
graffiti	Build media tags editor plugin
guess	Enable tags encoding guessing via the libguess library
mp3tunes	Build plugin for supporting the mp3tunes.com music locker service
mpris	Enable MPRIS support
potorchu	Enable the projectM-based visualization effects module for LMP

lc-monocle

fb2	Enable support for FictionBook format
mobi	Enable support for MOBI format

lc-musiczombie

acoustid	Use media-libs/chromaprint for acoustic fingerprinting

lc-netstoremanager

dropbox	Build Dropbox storage backend
googledrive	Build Google Drive storage backend

lc-poshuku

autosearch	Provide automatic search suggestions for Poshuku.
cleanweb	Build CleanWeb for ad blocking compatible with Firefox's AdBlock+.
dcac	Build color inverter module providing a night mode.
fatape	Build FatApe, GreaseMonkey userscripts support layer.
filescheme	Build FileScheme for accessing local URLs.
foc	Build FOC for Flash-on-Click functionality.
fua	Build FUA for faking user agents for different hosts.
keywords	Build Keywords for adjusting search shortcuts.
onlinebookmarks	Build OnlineBookmarks for syncing bookmarks with social bookmarking services like Read It Later.
qrd	Build module for displaying the QR code of a web page.
speeddial	Build SpeedDial module.
webengine	Build WebEngine- (that is, Chromium-)based rendering backend.

lc-secman

exposecontents	Build the GUI for viewing the stored data.

leechcraft-meta

de	Install components, that allow using Leechcraft as Desktop Environment

app-misc

anki

recording	Enable support for audio recording
sound	Enable support for adding sound to cards

bijiben

zeitgeist	Build the plugin to inject events to gnome-extra/zeitgeist

binwalk

graph	Enable support for generating entropy graphs

blink1

mini-tool	Build and install command-line mini-tool blink1-mini-tool (normally used for embedded devices)
server	Build and install REST API server (currently hard-coded to TCP port 8080)
tool	Build and install command-line tool blink1-tool

byobu

screen	Use app-misc/screen as the default backend

ca-certificates

cacert	Include root certificates from CAcert (http://www.cacert.org/) and Software in the Public Interest (http://www.spi-inc.org/)
insecure_certs	Install certificates which are known to be untrustworthy.

carbon-c-relay

lz4	add support for LZ4 compressed transport

ddccontrol

pci	enable direct PCI memory access (the setuid ddcpci util)

ddcutil

usb-monitor	Adds support for monitors attached via USB.
user-permissions	Adds a udev rules to allow non-root users in the i2c group to access the /dev/i2c-* devices. If usb-monitor is selected, users will need to be added to the video group to access the USB monitor. Otherwise, only root will be able to use ddcutil.

digitemp

ds2490	Build support for the ds2490 sensor
ds9097	Build support for the ds9097 sensor
ds9097u	Build support for the ds9097u sensor

emelfm2

ansi	Add support for ANSI escape sequences
gtk3	Use x11-libs/gtk+:3 instead of x11-libs/gtk+:2

freemind

groovy	Build plugin for scripting via Groovy
latex	Build plugin for inserting mathematical formulas in LaTeX syntax
pdf	Build plugin for exporting mindmaps to SVG and PDF
svg	Build plugin for exporting mindmaps to SVG and PDF

gcstar

stats	Enable statistics reporting
tellico	Enable support for kde-misc/tellico files

geoclue

geonames	Install geonames.org provider
gsmloc	Install GSM location provider
gtk	Install gtk-based geoclue-test-gui
hostip	Install hostip.info provder
manual	Install manual provider
modemmanager	Enable geolocation through 3G or GPS enabled hardware through net-misc/modemmanager.
nominatim	Install openstreetmap.org provider
plazes	Install plazes.com provider
skyhook	Install skyhookwireless.com provider
yahoo-geo	Install Yahoo geolocation provider
zeroconf	Enable retrieval of GPS location from Android devices with https://wiki.gnome.org/Apps/GeoclueShare

gourmet

i18n	Enable support for i18n through elib.intl
ipython	Enable support for the interactive Python console plugin
pdf	Enable export to PDF
print	Enable pretty Python printing
spell	Enable support for the spell check plugin
web	Enable support for the web import plugin

gramps

geo	Enable rendering of geographical data using sci-geosciences/osm-gps-map
reports	All external software that is needed for graphical reports will be installed

graphlcd-base

g15	Add support for app-misc/g15daemon driver (e.g. Logitech G15 Keybord)

irtrans-irserver

mono	Enable mono support

jq

oniguruma	Use dev-libs/oniguruma for regular expression support

lcd4linux

mpd	Add support for display of mpd controlled music (media-libs/libmpd)

lcdproc

ftdi	Enable support for FTDI connections in some selected LCD_DEVICES (currently hd44780)
hid	Enable HID support using libhid
irman	Enable support for IRMan (media-libs/libirman)
lcd_devices_sdeclcd	Enable support for VLSYS M428 display
lcd_devices_vlsys_m428	Enable support for VLSYS M428 display
nfs	Adds support for NFS file system
seamless-hbars	Try to avoid gaps in horizontal bars

lirc

audio	Support using an audio device connected to an IR receiver
devinput	Support the devinput input device
ftdi	Support FTDI devices
gtk	Include GTK support which enables the use of lirc-setup
hardware-carrier	The transmitter device generates its clock signal in hardware
iguanair	Support iguanaIR devices
inputlirc	Add a dependency on app-misc/inputlircd
irman	Add a dependency on media-libs/libirman
transmitter	Add transmitter support to some lirc-drivers (e.g. serial)
uinput	Enable support for uinput

mc

edit	Compile and install the mcedit application
mclib	Compile and install the libmc.so shared library
sftp	Add support for sftp (uses net-libs/libssh2 for it).
slang	Use sys-libs/slang instead of sys-libs/ncurses.
xdg	Toggles mc's config dir location. Enable for $XDG_CONFIG_HOME/mc, disable for $HOME/.mc

mosquitto

bridge	Enable bridge support in the MQTT broker.
persistence	Store messages and subscriptions to a file.
srv	Include SRV lookup support.
websockets	Support the WebSocket protocol.

muttprint

doc	Builds documentation

neofetch

X	Enable support for detecting DEs, WMs, screen resolutions, and showing images from an X terminal

note

general	Add support for ascii flatfile backend
text	Add support for text backend

openastro

jpeg	Enable exporting Astrological Charts to jpeg
png	Enable exporting Astrological Charts to png

pax-utils

python	Install a more powerful/faster version of lddtree

recoll

camelcase	Enable indexing for camelCase sentences and words
inotify	Use the Linux Kernel notification subsystem for monitoring file alterations in realtime
session	Stop monitoring file alterations when X11 session terminates

rlwrap

debug	Enable debug

screen

multiuser	Enable multiuser support (by setting correct permissions)
nethack	Express error messages in nethack style
utmp	Include utmp support

screenfetch

X	Use the media-gfx/scrot package to take screenshots

sphinx

id64	use 64-bit document and word IDs
re2	use the dev-libs/re2 regular expression library
stemmer	Enable language stemming support

task

sync	Enable "task sync" support

tasque

hiveminder	Allows you to use http://www.hiveminder.com/ as your storage backend.
rememberthemilk	Allows you to use http://www.rememberthemilk.com/ as your storage backend.

tmux

utempter	Include libutempter support

towitoko

moneyplex	Makes libtowitoko work for the moneyplex home banking software

tracker

cue	Enable cue sheet parsing
firefox-bookmarks	Install bookmark data miner plugin for www-client/firefox and www-client/firefox-bin
gsf	Enable gnome-extra/libgsf based data extractor and for ODT.
iptc	Enable extraction of IPTC data from pictures
iso	Enable extraction of metadata from ISO disk images
miner-fs	Enable tracker-miner-fs (required for filesystem indexing)
nautilus	Enable tracker to integrate with gnome-base/nautilus by providing entries in its context menu
playlist	Add support for playlists
stemmer	Add word stemming via dev-libs/snowball-stemmer.
thunderbird	Install email data miner plugin for mail-client/thunderbird and mail-client/thunderbird-bin
xps	Add support for XPS file format through app-text/libgxps.

unfoo

minimal	Do not install all support archive binaries

vifm

X	Add support for X11
compatibility	Compatibility with previous versions of vifm
developer	Enable features of interest to developers
extended-keys	Support for extended keys (arrows, home etc)
gtk	Use gtk+ to determine mimetypes
magic	Use libmagic to determine mimetypes
vim	Install the vifm vim plugin and vim-compatible documentation
vim-plugin	Install the vifm vim plugin
vim-syntax	Pulls in related vim syntax scripts

worker

avfs	Enable support for sys-fs/avfs
magic	Add magic file support from sys-apps/file to automatically detect file types

workrave

mate	Add support for MATE panel
xfce	Add support for XFCE panel

zygrib

maps	Installs additional GSHHS maps for high resolution coastline data and cities

app-mobilephone

gammu

bluetooth	Enables bluetooth support
curl	Enables curl support
irda	Enables infrared support
mysql	Use mysql for data storage
nls	Enable native language support
odbc	Use ODBC as DB connector
postgres	Use PostgreSQL for data storage
usb	Enable USB suport

gnokii

ical	Enable support for dev-libs/libical
irda	Enable infrared support
pcsc-lite	Enable smartcard support with sys-apps/pcsc-lite
sms	Enable SMS support (build smsd)

smstools

stats	Enable statistic reporting

app-office

abiword

collab	Enable collaborative editing plugin
goffice	Enable goffice plugin
grammar	Enable grammar checking via dev-libs/link-grammar
map	Enable world map support through media-libs/libchamplain
math	Enable support for x11-libs/gtkmathview
ots	Enable Text Summarizer plugin
plugins	Enable plugins build (see http://www.abisource.com/wiki/PluginMatrix for more information). If your file cannot be opened due lack of support, try enabling this.
redland	Enables support redland and raptor libs.
thesaurus	Enable thesaurus support
wordperfect	Enable wordperfect file support via app-text/libwpd

calligra

activities	Enable kactivities support
import-filter	Enable support for various import filter file formats like WordPerfect, Visio and Apple Keynote
lcms	Build colorengine plugins using media-libs/lcms
okular	Enable bindings for kde-apps/okular
phonon	Build stage/eventplugins and videoshape plugin using media-libs/phonon
pim	Enable support for KDE PIM resources integration
spacenav	Enable support for the 3Dconnexion spacenav input device via dev-libs/libspnav

glabels

barcode	Enable barcode support through external libraries.

gnucash

chipcard	Enable support for chipcard reading and processing.
hbci	Enable HBCI support, for connecting to some internet banks
quotes	Enable Online Stock Quote retrieval

gnumeric

libgda	Enable database support through gnome-extra/libgda.
perl	Enable perl plugin loader.
python	Enable python plugin loader.

kexi

marble	Enable displaying of maps using kde-apps/marble
mdb	Enable support for Microsoft Access database
webkit	Enable web form designer widget using dev-qt/qtwebkit

kmymoney

hbci	Enable HBCI support using net-libs/aqbanking
quotes	Enable Online Stock Quote retrieval
weboob	Enable import of online banking transactions extracted by www-client/weboob

kraft

pim	Enable support for KDE PIM resources integration

libreoffice

coinmp	Use sci-libs/coinor-mp as alternative solver
collada	Enable Collada for rendering 3D models stored in *.dae and *.kmz format
gltf	Use media-libs/libgltf for inserting 3D models in the glTF format into presentations
googledrive	Enable support for remote files on Google Drive
gtk3	Enable highly experimental gtk3 frontend
jemalloc	Use dev-libs/jemalloc for allocations
odk	Build the Office Development Kit
pdfimport	Enable PDF import via the Poppler library
quickstarter	Build the system tray quickstarter
vlc	Use media-video/vlc for video embedding

libreoffice-l10n

offlinehelp	Install help files locally instead of using the LibreOffice Wiki

lyx

aspell	Add support for aspell spellchecking
dia	Add support for diagrams (app-office/dia)
docbook	Add support for docbook export
dot	Add support for DOT import (media-gfx/graphviz)
enchant	Add support for enchant spellchecking wrapper (both aspell and hunspell can be used by LyX).
gnumeric	Add support for importing Gnumeric/OpenOffice/MS Excel spreadsheets into LyX.
html	Add support for HTML import
hunspell	Add support for spellchecking based on hunspell and reuse system-wide OpenOffice dictionaries. This also enable thesaurus dictionaries not accessible via aspell.
monolithic-build	This should speed up compilation significantly when you have enough RAM (> 600 MB)
rcs	Add support for revision control via dev-vcs/rcs
rtf	Add support for RTF import/export packages

magicpoint

contrib	Install additional contributed scripts

orage

clock-panel-plugin	Build the clock plugin for the XFCE panel

scribus

boost	Enable support for Boost based enhancement
hunspell	Enable support for spell checking with app-text/hunspell
minimal	Don't install headers (only required for e.g. plug-in developers)
osg	3D redering via dev-games/openscenegraph
scripts	Install the scripts
templates	Document tamplates
tk	Install tk based scripts e.g. FontSample.py

skrooge

activities	Enable kactivities support
designer	Build plugins for dev-qt/designer

texmacs

netpbm	Add support for media-libs/netpbm
pdf	Add the experimental native pdf export

texstudio

video	Use phonon for video embedding

wps-office

sharedfonts	Install WPS fonts available system wide

app-pda

barry

boost	Enable boost support
desktop	Install the GUI desktop control panel
gui	Install the GUI backup tool

gtkpod

clutter	Enable clutter support for displaying coverart

app-portage

conf-update

colordiff	Use colors when displaying diffs (app-misc/colordiff)
libressl	Enable SSL connections and crypto functions using dev-libs/libressl

eix

debug	Build with upstream's CXXFLAGS/LDFLAGS for debugging support; not recommended for normal use.
doc	Create description of the eix cache file additionally in html format
sqlite	Compile in support for portage's sqlite backend; to actually use it you need additional configuration of portage and eix

g-sorcery

bson	Support BSON file format for package DB

gemato

blake2	Install dependencies needed for BLAKE2 hash functions
gpg	Install dependencies needed for OpenPGP signature verification support
portage-postsync	Install a Portage hook to verify the repository after fetching via rsync
sha3	Install dependencies needed for SHA3 hash functions

grs

server	Install all the tools building systems

layman

bazaar	Support dev-vcs/bzr based overlays
cvs	Support dev-vcs/cvs based overlays
darcs	Support dev-vcs/darcs based overlays
g-sorcery	Support app-portage/g-sorcery based overlays
git	Support dev-vcs/git based overlays
gpg	Support app-crypt/gnupg signed overlays lists and manifests
mercurial	Support dev-vcs/mercurial based overlays
squashfs	Support mounting squashfs image overlays locally read-only
subversion	Support dev-vcs/subversion based overlays
sync-plugin-portage	Install the sys-apps/portage sync module

pfl

network-cron	Adds a cron job which does a weekly submit of the package database

tatt

templates	Install template scripts to be used with tatt

app-shells

autojump

ipython	Add support for dev-python/ipython

bash

bashlogger	Log ALL commands typed into bash; should ONLY be used in restricted environments such as honeypots
mem-scramble	Build with custom malloc/free overwriting allocated/freed memory
net	Enable /dev/tcp/host/port redirection
plugins	Add support for loading builtins at runtime via 'enable'

dash

vanilla	Support echo -n, and enable echo -e all the time (unsupported)

mpv-bash-completion

luajit	Use dev-lang/luajit instead of dev-lang/lua

pdsh

rsh	This allows the use of rsh (remote shell) and rcp (remote copy) for authoring websites. sftp is a much more secure protocol and is preferred.

scsh-install-lib

scsh	Use a non-FHS directory layout

shish

diet	Use dev-libs/dietlibc

app-text

asciidoc

highlight	Enable source code highlighting

atril

caja	Enable property page extension in mate-base/caja
dvi	Enable build-in DVI viewer
epub	Enable build-in DVI viewer using net-libs/webkit-gtk
gtk3	Build with GTK+3 instead of GTK+2
t1lib	Enable the Type-1 fonts for the build-in DVI viewer (media-libs/t1lib)
xps	Enable XPS viewer using app-text/libgxps

blogc

git	Build blogc-git-receiver tool
httpd	Build blogc-runserver tool
make	Build blogc-make tool

cb2bib

webengine	Use dev-qt/qtwebengine instead of dev-qt/qtwebkit

coolreader

wxwidgets	Use x11-libs/wxGTK instead of Qt5

crm114

mew	Add support for using the mewdecode mime decoder (app-emacs/mew)
mimencode	Add support for using the mimencode mime (net-mail/metamail)
normalizemime	Add support for using the normalizemime (mail-filter/normalizemime)

dbacl

interactive	Enable the interactive mailinspect ability

dblatex

inkscape	Use inkscape to convert SVG. Disable to use gnome-base/librsvg instead.

dictd

judy	Build Judy-based (dev-libs/judy) plugin implementing fast "exact" and especially "lev" strategies
minimal	Don't build server but dict client, dictzip and dictfmt only.

docbook-sgml-utils

jadetex	Add support for app-text/jadetex (for processing tex files produced by the TeX backend of Jade)

docbook-xsl-ns-stylesheets

ruby	Install the Ruby-based dbtoepub script; requires an interpreter compatible with app-eselect/eselect-ruby.

docbook-xsl-stylesheets

ruby	Install the Ruby-based dbtoepub script; requires an interpreter compatible with app-eselect/eselect-ruby.

ebook-tools

lit2epub	Install lit2epub script

editorconfig-core-c

cli	Install command line interface.

enchant

aspell	Adds support for app-text/aspell spell checker
hunspell	Adds support for app-text/hunspell spell checker
zemberek	Adds support for app-text/zemberek-server spell checker server

evince

dvi	Enable the built-in DVI viewer
nautilus	Enable property page extension in gnome-base/nautilus
t1lib	Enable the Type-1 fonts for the built-in DVI viewer (media-libs/t1lib)
xps	Enable XPS viewer using app-text/libgxps

getxbook

ocr	Use app-text/tesseract for optical character recognition

ghostscript-gpl

unicode	Add support for unicode passwords via net-dns/libidn

glark

zip	Support for ZIP files using dev-ruby/rubyzip

groonga

abort	Enable query abortion
benchmark	Build benchmark programs
dynamic-malloc-change	Allow dynamic memory allocation change for testing
exact-alloc-count	Atomic counting for memory alloc count
fmalloc	Make memory allocation failed in specified condition for debug
futex	Use futex
libevent	Enable dev-libs/libevent used for suggestion
mecab	Use app-text/mecab for morphological analysis
msgpack	Enable dev-libs/msgpack used for suggestion
nfkc	Use nfkc based utf8 normalization
sphinx	Enable document generation by app-misc/sphinx
uyield	Build for detecting race conditions
zeromq	Enable net-libs/zeromq used for suggestion

gtranslator

gnome-dictionary	Enable plugin for dictionary lookups using app-dicts/gnome-dictionary.
gucharmap	Enable plugin for unicode symbols selection using gnome-extra/gucharmap.

hyperestraier

mecab	Enable app-text/mecab support for Estraier

kbibtex

webengine	Use dev-qt/qtwebengine for HTML previews
webkit	Use dev-qt/qtwebkit for HTML previews
zotero	Enable support for synchronisation with zotero.org web service

lcdf-typetools

kpathsea	Enable integration with kpathsea search library (TeX related)

libebook

tools	Build file conversion tools

libmwaw

tools	Build file conversion tools

libqxp

tools	Build file conversion tools

libstaroffice

tools	Build conversion tools
zlib	Enable support for compressed data

libwpd

tools	Build file conversion tools

libwps

tools	Build file conversion tools

mathtex

png	Generate png images by default instead of gif

mupdf

openssl	Use dev-libs/openssl crypto backend

pandoc

embed_data_files	Embed data files in binary for relocatable executable.
http-conduit	Enable downloading of resources over https.
https	Enable support for downloading of resources over https.
make-pandoc-man-pages	Build program to regenerate pandoc man pages from README.
network-uri	Get Network.URI from the network-uri package.
trypandoc	Build trypandoc cgi executable.
weigh-pandoc	Build weigh-pandoc to measure memory usage.

pastebinit

crypt	Install pbputs for gpg-encrypted pastes

pdfgrep

unac	Removing accents and ligatures before search

pelican

markdown	Markdown support

podofo

boost	Add support for boost
tools	Build and install commandline tools.

poppler

nss	Enable signatures handling with dev-libs/nss
utils	Install command-line PDF converters and various utilities.

qpdf

perl	Install fix-qdf tool (for reverting PDF edits) written in perl

qpdfview

fitz	Use experimental fitz rendering, provided by app-text/mupdf, instead of poppler
synctex	Add support for searching TeX sources

sdcv

darkterm	Improve readability of color output on terminals with dark background.

sgmltools-lite

jadetex	Add support for app-text/jadetex (for processing tex files produced by the TeX backend of Jade)

stardict

advertisement	Enable stardict advertisements plugin
cal	Enable calendar support using cal program
dictdotcn	Enable dict.cn network plugin (for Chinese language)
espeak	Enable text to speech synthesizer plugin using app-accessibility/espeak engine
flite	Enable text to speech synthesizer plugin using app-accessibility/flite engine
fortune	Enable plugin to read fortune messages using games-misc/fortune-mod. You may consider installing games-misc/fortune-mod-all to get all fortune messages.
gucharmap	Enable plugin for unicode symbols description using gnome-extra/gucharmap
htmlparse	Enable plugin to parse dictionaries with html content
info	Enable plugin to read info pages
man	Enable plugin to read manual pages
powerwordparse	Enable plugin to parse powerword dictionaries
pronounce	Install WyabdcRealPeopleTTS package (it is just many .wav files) to make StarDict pronounce English words
qqwry	Enable QQWry plugin, which provides information (in Chinese language) about geographical positions, owner, etc. for IP addresses
tools	Build and install dictionary management tools and converters from various dictionary formats
updateinfo	Enable plugin to check for stardict updates
wikiparse	Enable plugin to parse dictionaries in wikimedia format
wordnet	Enable wordnet plugin to find similar English words using lexical database
xdxfparse	Enable plugin to parse dictionaries in xdxf (XML Dictionary eXchange Format)
youdaodict	Enable youdao.com network plugin (for Chinese language)

sword

clucene	Use dev-cpp/clucene for lucene search support

tesseract

math	Enable support for recognition of equations.
opencl	Enable opencl support for speedup using GPU computation.
osd	Enable support orientation and script detection.
scrollview	Install viewer to debug recognition (ScrollView).
training	Install training applications to add support for new languages.
webp	Enable support for webp image format.

texlive

context	Add support for the ConTeXt format (dev-texlive/texlive-context)
detex	Add support for dev-tex/detex, a filter program that removes the LaTeX (or TeX) control sequences
dvi2tty	Add support for dev-tex/dvi2tty to preview dvi-files on text-only devices
epspdf	Add support for app-text/epspdf, a tool for converting [e]ps files to pdf
extra	Add support for extra TeXLive packages
games	Add typesetting support for games (chess, etc.) (dev-texlive/texlive-games)
graphics	Add support for several graphics packages (pgf, tikz,...)
humanities	Add LaTeX support for the humanities (dev-texlive/texlive-humanities)
jadetex	Add support for app-text/jadetex (for processing tex files produced by the TeX backend of Jade)
luatex	Add extra support for luatex
metapost	Add support for metapost: A tool for creating graphics in scalable PostScript
music	Add support for music typesetting (dev-texlive/texlive-music)
omega	Add omega packages (dev-texlive/texlive-omega)
pdfannotextractor	Add dev-tex/pdfannotextractor support, for extracting annotations from PDF files
pstricks	Add pstricks packages (dev-texlive/texlive-pstricks)
publishers	Add support for publishers (dev-texlive/texlive-publishers)
science	Add typesetting support for natural and computer sciences (dev-texlive/texlive-science)
tex4ht	Add support for dev-tex/tex4ht (for converting (La)TeX to (X)HTML, XML and OO.org)
texi2html	Add support for app-text/texi2html which converts texi files to HTML
xetex	Add support for XeTeX macros (dev-texlive/texlive-xetex)
xindy	Add support for app-text/xindy, a flexible indexing system

texlive-core

luajittex	Add support for LuaJitTeX: LuaTeX based on LuaJIT which is usually faster.
xetex	Add support for XeTeX: a TeX system with Unicode and modern font technologies.

wdiff

experimental	Build experimental utilities (mdiff, unify, wdiff2)

webgen

builder	Enable programmatic HTML/XML generation
highlight	Enable syntax highlighting for certain plugins
markdown	Markdown support

wklej

vim	Install the vim plugin allowing to paste through ':Wklej'.

writerperfect

abiword	Add support for abiword format using app-text/libabw
ebook	Add support for various ebook formats using app-text/libebook
freehand	Add support for freehand format using media-libs/libfreehand
gsf	Add support for structured files using gnome-extra/libgsf
keynote	Add support for keynote format using app-text/libetonyek
mspub	Add support to mspub format using app-text/libmspub
mwaw	Add support to mwaw formats using app-text/libmwaw
pagemaker	Add support to pagemaker formats using media-libs/libpagemaker
visio	Add support for visio format using media-libs/libvisio
wpd	Add support for wpd format using app-text/libwpd
wpg	Add support for wpg format using app-text/libwpg
wps	Add support for wps format using app-text/libwps

wv

tools	Install optional utilities considered deprecated in favor of using AbiWord.

xmlto

text	Support conversion from XML to plain text

yagf

cuneiform	Enable support for the app-text/cuneiform OCR engine.
tesseract	Enable support for the app-text/tesseract OCR engine.

zathura

magic	Use libmagic to determine mimetypes
synctex	Use libsynctex to get latex codeline from pdf

zathura-meta

cb	Install plug-in for ComicBook support

app-vim

gentoo-syntax

ignore-glep31	Remove GLEP 31 (UTF-8 file encodings) settings

vim-latex

html	Install HTML documentation

youcompleteme

clang	Enable semantic support for C-family languages using sys-devel/clang

dev-ada

asis

gnat_2016	Compile with dev-lang/gnat-gpl-2016
gnat_2017	Compile with dev-lang/gnat-gpl-2017

aunit

gnat_2016	Compile with dev-lang/gnat-gpl-2016
gnat_2017	Compile with dev-lang/gnat-gpl-2017

aws

gnat_2016	Compile with dev-lang/gnat-gpl-2016
gnat_2017	Compile with dev-lang/gnat-gpl-2017

gnat_util

gnat_2016	Compile with dev-lang/gnat-gpl-2016
gnat_2017	Compile with dev-lang/gnat-gpl-2017
shared	Build gnat_util shared library
static	Build gnat_util static library
static-pic	Build gnat_util static library with pic code

gnatcoll

gnat_2016	Compile with dev-lang/gnat-gpl-2016
gnat_2017	Compile with dev-lang/gnat-gpl-2017
projects	Adds support for projects
pygobject	Adds support for pygobject
shared	Build shared library
static	Build static library
tools	Build associated tools

gnatmem

gnat_2016	Compile with dev-lang/gnat-gpl-2016
gnat_2017	Compile with dev-lang/gnat-gpl-2017

gprbuild

gnat_2016	Compile with dev-lang/gnat-gpl-2016
gnat_2017	Compile with dev-lang/gnat-gpl-2017

gtkada

gnat_2016	Compile with dev-lang/gnat-gpl-2016
gnat_2017	Compile with dev-lang/gnat-gpl-2017
shared	Build gtkada as shared library
static	Build gtkada as static library

libadalang

gnat_2016	Compile with dev-lang/gnat-gpl-2016
gnat_2017	Compile with dev-lang/gnat-gpl-2017

libgpr

gnat_2016	Compile with dev-lang/gnat-gpl-2016
gnat_2017	Compile with dev-lang/gnat-gpl-2017
shared	Build shared library
static	Build static library
static-pic	Build static library with pic code

xmlada

gnat_2016	Compile with dev-lang/gnat-gpl-2016
gnat_2017	Compile with dev-lang/gnat-gpl-2017
shared	Build shared library
static	Build static library
static-pic	Build static library with pic code

dev-cpp

eigen

c++11	Build using the C++11 standard
cuda	Build with cuda support

glog

gflags	Use dev-cpp/gflags for flag parsing
unwind	Use sys-libs/libunwind for stack unwinding instead of glibc/gcc (may be more reliable on x86_64)

libcmis

man	Build and install man pages.

libjson-rpc-cpp

http-client	Build support for HTTP client using net-misc/curl
http-server	Build support for HTTP server using net-libs/libmicrohttpd
redis-client	Build support for Redis client using dev-libs/hiredis
redis-server	Build support for Redis server using dev-libs/hiredis
stubgen	Build header stub code generator (needed for development and when pregenerated headers are not bundled)

pficommon

fcgi	Build FCGI feature
mprpc	Build MessagePack RPC feature

websocketpp

boost	Use dev-libs/boost instead of C++11

xsd

ace	Enable support for serializing to/from an ACE CDR stream

dev-db

aerospike-server-community

tools	Install extra tools

cppdb

mysql_internal	Don't build a separate mysql loadable module but rather build it into the cppdb library itself
odbc_internal	Don't build a separate postgresql loadable module but rather build it into the cppdb library itself
postgres_internal	Don't build a separate odbc loadable module but rather build it into the cppdb library itself
sqlite_internal	Don't build a separate sqlite3 loadable module but rather build it into the cppdb library itself

firebird

server	Install the server components of Firebird, not just the client
superserver	Install SuperServer
xinetd	Install ClassicServer

maatkit

udf	Build the MySQL UDFs shipped with maatkit, requires non-minimal MySQL

mariadb

backup	Build mariadb-backup which supports SST and hot backup of InnoDB, Aria and MyISAM including compression and encryption
cluster	Add support for NDB clustering (deprecated)
community	Enables the community features from upstream.
embedded	Build embedded server (libmysqld)
extraengine	Add support for alternative storage engines (Archive, CSV, Blackhole, Federated(X), Partition)
galera	Enables galera replication
innodb-lz4	Enables lz4 compression methods for InnoDB/XtraDB
innodb-lzo	Enables lzo compression methods for InnoDB/XtraDB
innodb-snappy	Enables snappy compression methods for InnoDB/XtraDB using app-arch/snappy
jdbc	Enable the CONNECT engine to access foreign databases via JDBC
jemalloc	Use dev-libs/jemalloc for allocations.
latin1	Use LATIN1 encoding instead of UTF8
libressl	Enable SSL connections and crypto functions using dev-libs/libressl
max-idx-128	Raise the max index per table limit from 64 to 128
minimal	Install client programs only, no server
mroonga	Add support for the Mroonga engine for interfacing with the Groonga text search
numa	Enable NUMA support using sys-process/numactl (NUMA kernel support is also required)
openssl	Enable SSL connections and crypto functions using dev-libs/openssl
oqgraph	Add support for the Open Query GRAPH engine
pam	Enable the optional PAM authentication plugin for the server
profiling	Add support for statement profiling (requires USE=community).
rocksdb	Add support for RocksDB; a key/value, LSM database optimized for flash storage
server	Build the server program
sphinx	Add suport for the sphinx full-text search engine
sst-mariabackup	Add tools needed to support the mariabackup SST method
sst-rsync	Add tools needed to support the rsync SST method
sst-xtrabackup	Add tools needed to support the xtrabackup and xtrabackup-v2 SST methods
systemtap	Build support for profiling and tracing using dev-util/systemtap
test	Install upstream testsuites for end use.
tokudb	Add support for TokuDB storage engine
yassl	Enable SSL connections and crypto functions using the bundled yaSSL

mariadb-galera

embedded	Build embedded server (libmysqld)
extraengine	Add support for alternative storage engines (Archive, CSV, Blackhole, Federated(X), Partition)
jdbc	Enable the CONNECT engine to access foreign databases via JDBC
jemalloc	Use dev-libs/jemalloc for allocations.
latin1	Use LATIN1 encoding instead of UTF8
libressl	Enable SSL connections and crypto functions using dev-libs/libressl
openssl	Enable SSL connections and crypto functions using dev-libs/openssl
oqgraph	Add support for the Open Query GRAPH engine
profiling	Add support for statement profiling (requires USE=community).
server	Build the server program
sphinx	Add suport for the sphinx full-text search engine
sst-rsync	Add tools needed to support the rsync SST method
sst-xtrabackup	Add tools needed to support the xtrabackup and xtrabackup-v2 SST methods
systemtap	Build support for profiling and tracing using dev-util/systemtap
test	Install upstream testsuites for end use.
tokudb	Add support for TokuDB storage engine
yassl	Enable SSL connections and crypto functions using the bundled yaSSL

maxscale

jemalloc	Use dev-libs/jemalloc for allocations
rabbitmq	Add support for RabbitMQ message queue

mongodb

mms-agent	Install the MongoDB Monitoring Service agent
tools	Install the MongoDB tools (mongoimport, mongodump...) from app-admin/mongo-tools

mysql

cluster	Add support for NDB clustering (deprecated)
community	Enables the community features from upstream.
embedded	Build embedded server (libmysqld)
extraengine	Add support for alternative storage engines (Archive, CSV, Blackhole, Federated(X), Partition)
jemalloc	Use dev-libs/jemalloc for allocations.
latin1	Use LATIN1 encoding instead of UTF8
libressl	Enable SSL connections and crypto functions using dev-libs/libressl
max-idx-128	Raise the max index per table limit from 64 to 128
minimal	Install client programs only, no server
numa	Enable NUMA support using sys-process/numactl (NUMA kernel support is also required)
openssl	Enable SSL connections and crypto functions using dev-libs/openssl
profiling	Add support for statement profiling (requires USE=community).
server	Build the server program
systemtap	Build support for profiling and tracing using dev-util/systemtap
test	Install upstream testsuites for end use.
yassl	Enable SSL connections and crypto functions using the bundled yaSSL

mysql-cluster

cluster	Add support for NDB clustering
community	Enables the community features from upstream.
embedded	Build embedded server (libmysqld)
extraengine	Add support for alternative storage engines (Archive, CSV, Blackhole, Federated(X), Partition)
jemalloc	Use dev-libs/jemalloc for allocations.
latin1	Use LATIN1 encoding instead of UTF8
libressl	Enable SSL connections and crypto functions using dev-libs/libressl
max-idx-128	Raise the max index per table limit from 64 to 128
minimal	Install client programs only, no server
numa	Enable NUMA support using sys-process/numactl (NUMA kernel support is also required)
openssl	Enable SSL connections and crypto functions using dev-libs/openssl
profiling	Add support for statement profiling (requires USE=community).
server	Build the server program
systemtap	Build support for profiling and tracing using dev-util/systemtap
test	Install upstream testsuites for end use.
yassl	Enable SSL connections and crypto functions using the bundled yaSSL

mysql-connector-c++

gcov	Build coverage support

oracle-instantclient

jdbc	Support for XA, Internationalization, and RowSet operations under JDBC
odbc	Libraries for enabling ODBC applications
sdk	Header files and an example makefile for developing Oracle applications
sqlplus	Libraries and executable for running SQL*Plus
tools	Workload Replay Client

percona-server

embedded	Build embedded server (libmysqld)
extraengine	Add support for alternative storage engines (Archive, CSV, Blackhole, Federated(X), Partition)
jemalloc	Use dev-libs/jemalloc for allocations.
latin1	Use LATIN1 encoding instead of UTF8
libressl	Enable SSL connections and crypto functions using dev-libs/libressl
numa	Enable NUMA support using sys-process/numactl (NUMA kernel support is also required)
openssl	Enable SSL connections and crypto functions using dev-libs/openssl
profiling	Add support for statement profiling (requires USE=community).
server	Build the server program
systemtap	Build support for profiling and tracing using dev-util/systemtap
test	Install upstream testsuites for end use.
tokudb	Add support for TokuDB storage engine
tokudb-backup-plugin	Builds the TokuDB backup plugin
yassl	Enable SSL connections and crypto functions using the bundled yaSSL

pgadmin3

databasedesigner	Enable the Database Designer component

pgbouncer

c-ares	Use c-ares as the DNS backend instead of evdns (libevent).
libevent	Use libevent 2.0+ and evdns as the DNS backend
udns	Use udns as the DNS backend instead of evdns (libevent). Supports IPv4 only.

pgpool2

memcached	Use memcached for query caching.

pgrouting

drivingdistance	Enable to calculate driving distance
html	Install HTML formatted documentation

phpmyadmin

setup	Installs the phpMyAdmin setup utility. Users who don't use the utility should disable this USE flag for security reasons as the setup tool was the target of various exploits in the past.

postgis

address-standardizer	Normalize US and CA postal addresses
gtk	Build graphical interface for shp2pgsql (shp2pgsql-gui)
mapbox	Add capability to transform geometry into Mapbox Vector Tile
topology	Build topology spatial types and functions

postgresql

pg_legacytimestamp	Use double precision floating-point numbers instead of 64-bit integers for timestamp storage.
server	Disable to build and install the clients and libraries only.
uuid	Enable server side UUID generation (via dev-libs/ossp-uuid).

psqlodbc

iodbc	Use dev-db/libiodbc. Disable to use dev-db/unixODBC.

redis

jemalloc	Use dev-libs/jemalloc for allocations.
luajit	Use dev-lang/luajit instead of dev-lang/lua
tcmalloc	Use tcmalloc from dev-util/google-perftools for allocations.

rethinkdb

jemalloc	Use dev-libs/jemalloc for allocations (default).
tcmalloc	Use tcmalloc from dev-util/google-perftools for allocations.

soci

boost	Enable boost support
empty	Build the sample backend called Empty

spatialite

geos	Add the sci-libs/geos library for exact topological tests
proj	Add the sci-libs/proj library for reprojection features
xls	Add the dev-libs/freexl library for xls import support

sqlite

secure-delete	Enable overwriting of deleted content with zeros by default (http://sqlite.org/pragma.html#pragma_secure_delete), causing some performance penalty
tools	Install additional tools

sqlitestudio

cli	Build CLI interface

tokumx

pax_kernel	Apply patch needed for hardened kernels

unixODBC

minimal	Disable bundled drivers and extra libraries (most users don't need these)
odbcmanual	Administrator, Internal Structure, Programmer and User documentation

dev-embedded

avrdude

ftdi	Enable support for USB FTDI chips via dev-embedded/libftdi

libftdi

tools	build ftdi_eeprom helper tool

openocd

cmsis-dap	Support for CMSIS-DAP compliant adapters
dummy	Build the dummy port driver
ftdi	Enable support for USB FTDI chips via dev-embedded/libftdi
jlink	Build the SEGGER J-Link driver
parport	Enable support for parport JTAG devices
verbose-io	Verbose IO and comm JTAG and USB messages

sdcc

boehm-gc	Enable Hans Boehm's garbage collector dev-libs/boehm-gc
device-lib	Enable built of devices libraries
ds390	Add support for Dallas DS390
ds400	Add support for Dallas DS400
gbz80	Add support for Gameboy gbz80
hc08	Add support for Freescale/Motorola HC08 based
mcs51	Add support for Intel mcs51
non-free	Enable non-free runtime library parts
packihx	Enable Intel HEX files pack utility
pic14	Add support for Microchip 14 bits PICs
pic16	Add support for Microchip 16 bits PICs
r2k	Add support for Rabbit 2000
r3ka	Add support for Rabbit 3000A
s08	Add support for Freescale/Motorola S08
sdbinutils	Enable SDCC library archive utilities sdar, sdranlib, sdnm
sdcdb	Enable SDCC source level debugger
sdcpp	Enable SDCC preprocessor based on GCC cpp
stm8	Add support for STMicroelectronics STM8
tlcs90	Add support for TLCS-90
ucsim	Enable software simulator for microcontrollers
z180	Add support for Zilog Z180
z80	Add support for Zilog Z80

urjtag

ftd2xx	Enable support for USB FTDI chips via dev-embedded/libftd2xx
ftdi	Enable support for USB FTDI chips via dev-embedded/libftdi

dev-games

aseprite

bundled-libs	Use the upstream provided bundled version of allegro 4.4.2
gtk3	Enable support for the experimental native GTK File Dialog
webp	Enable webp image format support

cegui

devil	Build the DevIL based ImageCodec module
freeimage	Build the FreeImage based ImageCodec module
irrlicht	Enable the Irrlicht renderer
ogre	Enable the OGRE renderer
tinyxml	Enable the Tiny XML parser module
xerces-c	Enable the Xerces-C++ XML parser module
zip	Enable the Minizip resource provider

crystalspace

3ds	Enables support for .3DS files in CrystalSpace
bullet	include support for Bullet library
cal3d	include support for skeleton animation
cegui	include support for Crazy Eddie GUI
cg	NVIDIA toolkit plugin
ode	include support for Open Dynamics Engine

guichan

allegro	Build the Allegro frontend

mygui

linguas_ru	Install some additional russian docs if 'doc' useflag enabled
ogre	Use the ogre render subsystem. (cannot combine with opengl)
opengl	Use the opengl render subsystem. (cannot combine with ogre)
plugins	Build MyGUI plugins
samples	Install MyGUI demos (needs ogre USE flag)
tools	Build the tools for development

ode

double-precision	more precise calculations at the expense of speed
gyroscopic	enable gyroscopic term (may cause instability)

ogre

boost	enable boost support
cg	NVIDIA toolkit plugin
double-precision	more precise calculations at the expense of speed
freeimage	support images via freeimage
gl3plus	Build OpenGL 3+ RenderSystem (EXPERIMENTAL)
gles2	build OpenGL ES 2.x RenderSystem
gles3	Enable OpenGL ES 3.x Features
ois	pull in Object-oriented Input System library for samples
poco	when USE=threads, use poco for threading
tbb	when USE=threads, use tbb for threading
tools	build+install helper tools
zip	support zip archives

openscenegraph

asio	Enable support for dev-cpp/asio library
fox	Build examples using x11-libs/fox library
gdal	Enable support for sci-libs/gdal library
las	Enable support for geospatial data LAS LiDAR format using sci-geosciences/liblas
openinventor	Build OpenInventor plugin
osgapps	Build osg applications
sdl2	Use media-libs/libsdl2 additionally to media-libs/libsdl
xrandr	Enable support for the X xrandr extension

physfs

grp	Enable Build Engine GRP archive support
hog	Enable Descent I/II HOG archive support
mvl	Enable Descent I/II MVL archive support
qpak	Enable Quake I/II QPAK archive support
wad	Enable Doom WAD archive support
zip	Enable ZIP archive support

simgear

dns	Enable DNS resolver via net-libs/udns
gdal	Enable alternative terrain engine based on pagedLOD via sci-libs/gdal
subversion	Enable terrasync scenery downloader

dev-haskell

abstract-deque

usecas	Enable the reference implementation to use hardware compare-and-swap.

aeson-pretty

lib-only	don't build 'aeson-pretty' executable.

ansi-terminal

example	Build the example application.

ansi-wl-pprint

example	Build the example application.

authenticate

network-uri	Get Network.URI from the network-uri package

bifunctors

semigroups	You can disable the use of the `semigroups` package using `-f-semigroups`. Disabing this is an unsupported configuration, but it may be useful for accelerating builds in sandboxes for expert users.
tagged	You can disable the use of the `tagged` package using `-f-tagged`. Disabing this is an unsupported configuration, but it may be useful for accelerating builds in sandboxes for expert users.

biosff

fclip	Build the fclip executable.
flower	Build the flower executable.
frecover	Build the frecover executable.

blaze-builder-enumerator

newbuilder	use bytestring-builder instead of blaze-builder-0.3

bytedump

executable	build executable file

bytes

test-doctests	Enable the doctest suite when using the enable-tests option for cabal.

c2hs

regression	run regression tests

cabal-install

network-uri	Get Network.URI from the network-uri package.
noprefs	Ignore 'preferred-versions' file from hackage's tarball.

certificate

executable	Build the executable

cgi

extensible-exceptions-in-base	Required to be enabled for >=dev-lang/ghc-7.
network-uri	Get Network.URI from the network-uri package.

chell

color-output	use colors in program output

citeproc-hs

bibutils	use Chris Putnam's app-text/bibutils
embed_data_files	Embed locale files into the library (needed for windows packaging)
hexpat	use dev-haskell/hexpat instead of dev-haskell/xml for XML parsing
network	use dev-haskell/network and dev-haskell/http to retrieve CSL file from URIs
small_base	Choose the new smaller, split-up base package.
unicode_collation	Use Haskell bindings to the dev-libs/icu

cmark

system-cmark	use app-text/cmark instead of bundled copy

cmdargs

quotation	Build quote module
testprog	Build the test program

comonad

containers	You can disable the use of the `containers` package using `-f-containers`. Disabing this is an unsupported configuration, but it may be useful for accelerating builds in sandboxes for expert users.
contravariant	You can disable the use of the `contravariant` package using `-f-contravariant`. Disabling this is an unsupported configuration, but it may be useful for accelerating builds in sandboxes for expert users. If disabled we will not supply instances of `Contravariant`
distributive	You can disable the use of the `distributive` package using `-f-distributive`. Disabling this is an unsupported configuration, but it may be useful for accelerating builds in sandboxes for expert users. If disabled we will not supply instances of `Distributive`
test-doctests	Run the doctests test suite

conduit

nohandles	experimental code to use raw system calls in place of handles. Not recommended for general use

configfile

buildtests	Build the executable to run unit tests.

contravariant

safe	Get Safe guarantees rather than merely Trustworthy, but with worse constant factors.
semigroups	You can disable the use of the `semigroups` package using `-f-semigroups`. Disabling this is an unsupported configuration, but it may be useful for accelerating builds in sandboxes for expert users.
statevar	You can disable the use of the `StateVar` package using `-f-StateVar`. Disabling this is an unsupported configuration, but it may be useful for accelerating builds in sandboxes for expert users.
tagged	You can disable the use of the `tagged` package on older versons of GHC using `-f-tagged`. Disabling this is an unsupported configuration, but it may be useful for accelerating builds in sandboxes for expert users.

cpu

executable	build 'cpuid' tool

crypto-api

all_cpolys	Build all the CMAC polynomes up to 10000 bits instead of just the usual ones

crypto-conduit

conduit11	Use conduit >= 1.1.

cryptohash

cryptoapi	Defines crypto-api instances

cryptonite

integer-gmp	Whether or not to use GMP for some functions
support_aesni	allow compilation with AESNI on system and architecture that supports it
support_blake2_sse	Use SSE optimized version of BLAKE2
support_deepseq	add deepseq instances for cryptographic types
support_pclmuldq	Allow compilation with pclmuldq on architecture that supports it
support_rdrand	allow compilation with AESNI on system and architecture that supports it

dav

network-uri	Get Network.URI from the network-uri package.

distributive

lib-werror	Compile with the ghc -Werror option

encoding

systemencoding	Provide the getSystemEncoding action to query the locale.

entropy

halvm	Build for the HaLVM.

filestore

maxcount	Make use of a recent (>= 2.3.0) Darcs feature which vastly improves the performance of 'latest'. You should disable this flag if you plan to use gitit with an older version of Darcs, or 'latest' will raise an error.

glib

closure_signals	Use the the GClosure-based signals implementation.

gtk

deprecated	Include definitions in this library that are considered obsolete.
fmode-binary	Set the default file translation mode for file I/O operations to _O_BINARY.
gio	Depend on GIO package, thereby enabling certain features.

gtk2hs-buildtools

closuresignals	Use the the GClosure-based signals implementation.

gtk3

fmode-binary	Set the default file translation mode for file I/O operations to _O_BINARY.
gio	Depend on GIO package, thereby enabling certain features.

hackage-security

use-network-uri	Get Network.URI from the network-uri package.

happstack-server

network-uri	Get Network.URI from the network-uri package
template_haskell	Description: Template Haskell is available on this system

hashed-storage

diff	Provide the Storage.Hashed.Diff module.
hpc	Compile with the profiling ghc flag -fhpc.

hashtables

bounds-checking	if on, use bounds-checking array accesses
portable	if on, use only pure Haskell code and no GHC extensions.
unsafe-tricks	turn on unsafe GHC tricks

haskeline

legacy-encoding	Use legacy iconv encoding for POSIX. This is only intended for testing.
libiconv	Explicitly link against the libiconv library.
terminfo	Use the terminfo package for POSIX consoles.

hdbc-odbc

buildstresstest	Build stress test

hdbc-sqlite3

buildtests	Build the executable to run unit tests
splitbase	Choose the new smaller, split-up package.

hexpat

bundled-expat	Use bundled expat instead of dev-libs/expat

highlighting-kate

executable	Build the Highlight executable.
pcre-light	Use the pcre-light library instead of regex-pcre-builtin.

hit

executable	Build the executable

hlint

gpl	Use GPL libraries, specifically hscolour.

hps

build-exec	Build the `hps-fractals' executable

hs3

network-uri	Get Network.URI from the network-uri package.

hslogger

buildtests	Build the executable to run unit tests.

hslua

apicheck	Compile Lua with -DLUA_USE_APICHECK..
system-lua	Use the system-wide lua instead of the bundled copy.

hsopenssl

fast-bignum	Enable fast moving of bignums between OpenSSL and GMP (GHC Only)

http

conduit10	Use version 1.0.x or below of the conduit package (for the test suite).
network-uri	Get Network.URI from the network-uri package.

http-api-data

use-text-show	Use text-show library for efficient ToHttpApiData implementations

http-client

network-uri	Get Network.URI from the network-uri package.

http-streams

network-uri	Get Network.URI from the network-uri package.

httpd-shed

buildexamples	Build example executables.
network-uri	Get Network.URI from the network-uri package.

hxt

network-uri	Get Network.URI from the network-uri package.

icalendar

network-uri	use network-uri package

json

generic	Add support for generic encoder (dev-haskell/syb)
mapdict	Encode Haskell maps as JSON dicts
parsec	Add support for parsing with Parsec
pretty	Add support for using pretty printing combinators

language-dot

executable	Build the `ppdot' executable

lens

benchmark-uniplate	Enable benchmarking against Neil Mitchell's uniplate library for comparative performance analysis. Defaults to being turned off to avoid the extra dependency.
dump-splices	Build and run the doctests test-suite.
inlining	Generate inline pragmas when using template-haskell. This defaults to enabled, but you can to shut it off to benchmark the relative performance impact, or as last ditch effort to address compile errors resulting from the myriad versions of template-haskell that all purport to be 2.8.
j	Attempt a parallel build with GHC 7.8.
lib-werror	Turn on ghc-options: -Werror
old-inline-pragmas	Some 7.6.1-rc1 users report their TH still uses old style inline pragmas. This lets them turn on inlining.
safe	Disallow unsafeCoerce
test-doctests	Build and run the doctests test-suite.
test-hlint	You can disable the hlint test suite with -f-test-hlint
test-hunit	You can disable the hunit test suite with -f-test-hunit
test-properties	Build the properties test if we're building tests
test-templates	Build the test templates if we're building tests
trustworthy	Assert that we are trustworthy when we can

lifted-async

monad-control-1	Use moand-control == 1.*

linear

template-haskell	You can disable the use of the `template-haskell` package using `-f-template-haskell`. Disabling this is an unsupported configuration, but it may be useful for accelerating builds in sandboxes for expert users.

monad-control

instancest	If enabled this package will export MonadBaseControl instances for the lazy and strict ST monad. If disabled these instances are only exported when base >= 4.4. If enabled it is required that the transformer-base package exports MonadBase instances for ST. It will do this by default.

monad-logger

template_haskell	Enable Template Haskell support.

monad-par

chaselev	Use Chase-Lev Deques for higher-perf work-stealing.

nats

hashable	You can disable the use of the `hashable` package using USE=-hashable. Disabling this is an unsupported configuration, but it may be useful for accelerating builds in sandboxes for expert users. If set we will not supply an instance of `Hashable`.

network-data

small_base	Build the split-up base package.

pandoc-citeproc

bibutils	use Chris Putnam's app-text/bibutils
embed_data_files	Embed locale files into the library (needed for windows packaging)
hexpat	use dev-haskell/hexpat instead of dev-haskell/xml for XML parsing
network	use dev-haskell/network and dev-haskell/http to retrieve CSL file from URIs
small_base	Choose the new smaller, split-up base package.
test_citeproc	Build the test-citeproc program
unicode_collation	Use Haskell bindings to the dev-libs/icu

persistent

nooverlap	Use OverlappingInstances only for String. Only developers should use this.

persistent-sqlite

build-sanity-exe	Build a sanity check test executable.

pointed

comonad	optional instances
containers	optional instances
kan-extensions	optional instances
semigroupoids	optional instances
semigroups	optional instances
stm	optional instances
tagged	optional instances
transformers	optional instances
unordered-containers	optional instances

publicsuffixlist

create	export Network.PublicSuffixList.Create module
runtimelist	read suffix list from dist at startup instead of embedding list into library

quickcheck

template_haskell	Enable additional test modules requiring Template Haskell support.

recaptcha

network-uri	Get Network.URI from the network-uri package.

reflection

template-haskell	Enable template haskell.

rfc5051

mkunicodedata	build codes generator itself

sandi

with-conduit	Build with conduit

scientific

bytestring-builder	Provide the Data.ByteString.Builder.Scientific module (requires bytestring >= 0.10).

semigroupoid-extras

profunctors	You can disable the use of the `profunctors` package using `-f-profunctors`. Disabing this is an unsupported configuration, but it may be useful for accelerating builds in sandboxes for expert users.

semigroupoids

comonad	You can disable the use of the `comonad` package using `-f-comonad`. Disabling this is an unsupported configuration, but it may be useful for accelerating builds in sandboxes for expert users. If disabled we will not supply instances of `Comonad`
containers	You can disable the use of the `containers` package using `-f-containers`. Disabing this is an unsupported configuration, but it may be useful for accelerating builds in sandboxes for expert users.
contravariant	You can disable the use of the `contravariant` package using `-f-contravariant`. Disabling this is an unsupported configuration, but it may be useful for accelerating builds in sandboxes for expert users. If disabled we will not supply instances of `Contravariant`
distributive	You can disable the use of the `distributive` package using `-f-distributive`. Disabling this is an unsupported configuration, but it may be useful for accelerating builds in sandboxes for expert users. If disabled we will not supply instances of `Distributive`
tagged	You can disable the use of the `tagged` package using `-f-tagged`. Disabing this is an unsupported configuration, but it may be useful for accelerating builds in sandboxes for expert users.

semigroups

binary	provide instances for binary package
bytestring	You can disable the use of the `bytestring` package using USE=-bytestring. Disabling this is an unsupported configuration, but it may be useful for accelerating builds in sandboxes for expert users.
containers	You can disable the use of the `containers` package using USE=-containers. Disabing this is an unsupported configuration, but it may be useful for accelerating builds in sandboxes for expert users.
deepseq	You can disable the use of the `deepseq` package using `-f-deepseq`. Disabing this is an unsupported configuration, but it may be useful for accelerating builds in sandboxes for expert users.
hashable	You can disable the use of the `hashable` package using USE=-hashable. Disabling this is an unsupported configuration, but it may be useful for accelerating builds in sandboxes for expert users. If set we will not supply an instance of `Hashable`.
text	You can disable the use of the `text` package using USE=-text. Disabling this is an unsupported configuration, but it may be useful for accelerating builds in sandboxes for expert users.
transformers	provide instances for transformers package.
unordered-containers	You can disable the use of the `unordered-containers` package using USE=-unordered-containers. Disabling this is an unsupported configuration, but it may be useful for accelerating builds in sandboxes for expert users.

sendfile

portable	Explicitly enable portable sendfile support (implemented in Haskell)

sha

exe	Build a sha1 and a sha384 executable similar to 'md5sum'.

shakespeare

test_coffee	Render tests through coffeescript render function.
test_export	Test export.
test_roy	Render tests through roy render function.

shakespeare-js

test_coffee	Test coffee.
test_export	Test export.
test_roy	Test roy.

shelly

lifted	run the tests against Shelly.Lifted

shuffle

network-uri	Get Network.URI from the network-uri package.

simple-sendfile

allow-bsd	Allow use of BSD sendfile (disable on GNU/kFreeBSD)

skein

big-endian	When manually selecting the endianness, use big-endian (default is little-endian)
force-endianness	Use a manually selected endian when compiling (see flag 'big-endian')
reference	Use the reference implementation instead of the optimized one

skylighting

executable	Build the skylighting executable.

snap-core

portable	No non-haskell unportable code.

snap-server

build-pong	Build a server that just returns "PONG"
openssl	enable https support using dev-haskell/hsopenssl
portable	no non-haskell unportable code.

tagsoup

download	Build with Download module.
testprog	Build the test program.

tasty

colors	Enable colorful output

tasty-quickcheck

old-quickcheck	Use Quick-Check < 2.7.

texmath

executable	Compile test executable.
network-uri	Get Network.URI from the network-uri package.

text

developer	operate in developer mode

thyme

bug-for-bug	bug-for-bug compatibility with time
lens	use the full lens package
show-internal	instance Show of internal representation

tls

compat	Accept SSLv2 compatible handshake.
network	Use the base network library.

transformers-base

orphaninstances	Build instances for orphan datatypes.

transformers-compat

three	Use transformers-0.3

unix-compat

old-time	build against old-time package

uuagc

bootstrap_external	Use an external uuagc executable for bootstrapping.
with-loag	Use dev-haskell/minisat external SAT-solver to schedule all Linear Ordered AGs.

vector

boundschecks	Enable bounds checking
internalchecks	Enable internal consistency checks at the cost of a significant performance penalty
unsafechecks	Enable bounds checking in unsafe operations at the cost of a significant performance penalty

vector-algorithms

bench	Build a benchmarking program.
boundschecks	Enable bounds checking.
internalchecks	Enable internal consistency checks at the cost of a significant performance penalty.
properties	Enable quickcheck tests.
unsafechecks	Enable bounds checking in unsafe operations at the cost of a significant performance penalty.

void

safe	dissable effective but unsafe coersions

wai-app-static

print	print debug info.

warp

allow-sendfilefd	Allow use of sendfileFd (not available on GNU/kFreeBSD).
warp-debug	Add additional debuging information

x11

screensaver	whether to build XScreenSaver.

x509-store

executable	Build the executable

xss-sanitize

network-uri	Get Network.URI from the network-uri package.

yaml

no-examples	don't build the examples
no-exe	don't install the yaml2json executable
no-unicode	Don't enable unicode output. Instead, unicode characters will be escaped.
system-libyaml	Use system libyaml instead on generic one

yesod-auth

network-uri	Get Network.URI from the network-uri package

yesod-form

network-uri	Get Network.URI from the network-uri package

zip-archive

executable	Build the Zip executable.

zlib

non-blocking-ffi	Execute FFI calls in the context of haskell thread.

dev-java

ant

antlr	Enable ANTLR Ant tasks
bcel	Enable bcel (bytecode manipulation) Ant tasks
commonslogging	Enable commons-logging Ant tasks
commonsnet	Enable commons-net Ant tasks
jai	Enable JAI (Java Imaging) Ant task
javamail	Enable JavaMail Ant task
jdepend	Enable Jdepend Ant tasks
jmf	Enable JMF (Java Media Framework) Ant tasks
jsch	Disable Jsch (ssh, scp and related) Ant tasks
log4j	Enable Apache log4j Ant tasks
oro	Enable Apache Oro Ant tasks
regexp	Enable Apache Regexp Ant tasks
resolver	Enable Apache Resolver Ant tasks
testutil	Enable optional test util classes

commons-collections

test-framework	Install the test framework

commons-logging

avalon-framework	Add optional support for avalon-framework
avalon-logkit	Add optional support for avalon-logkit
log4j	Add optional support for log4j
servletapi	Add optional support for servletapi

ecj-gcj

native	Build a native binary along with the jar. Provides faster execution time, but needs about 1G memory and some patience to compile.

eclipse-ecj

ant	Support using ecj in Ant builds via dev-java/ant-eclipse-ecj

emma

launcher	Install /usr/bin/emma. Collides with sci-biology/emboss.

gcj-jdk

awt	Install AWT libraries, needed by some GUIs (not needed to build icedtea)

gnu-classpath

alsa	Build with ALSA javax.sound.midi provider
dssi	Build with DSSI javax.sound.midi provider
gconf	Build with GConf preferences backend
gjdoc	Build GJDoc, a documentation generator
gmp	Build with GMP backend for java.math.BigInteger
gtk	Build with Gtk+ AWT peers
xml	Build with native XML backend

icedtea

cacao	Use the CACAO virtual machine rather than HotSpot.
cups	Link against the CUPS library at compile time, rather than using it dynamically at runtime.
headless-awt	Don't install the X backend for AWT, needed by some GUIs (used to be X flag)
jamvm	Use the JamVM virtual machine rather than HotSpot.
jbootstrap	If possible, recompile the final IcedTea executables with itself.
nsplugin	Enable browser plugin (NPPlugin), requires also the webstart flag to be enabled.
pax_kernel	Apply patch needed for pax enabled kernels.
shenandoah	Include the Shenandoah ultra-low pause time garbage collector (-XX:+UseShenandoahGC) (x86_64 only)
smartcard	Build the PCSC driver against pcsc-lite
sunec	Build the SunEC provider against system NSS
webstart	Enable Web Start support (via NetX).
zero	Enable Zero assembler port (usually for non-HotSpot architectures)

icedtea-bin

headless-awt	Don't install the X backend for AWT, needed by some GUIs (used to be X flag)
webstart	Provide javaws command through symlink to icedtea-web

icedtea-web

javascript	Enable support for using proxy auto config (PAC) files.
nsplugin	Enable the browser plugin (NPPlugin).
tagsoup	Depend on dev-java/tagsoup which allows parsing malformed .jnlp files

itext

rtf	Build and provide libraries for rich text format
rups	Build and provide GUI for Reading/Updating PDF Syntax

jcs

admin	Enable JCS Admin servlets

jdbc-mysql

c3p0	Enable c3p0 support
log4j	Enable log4 support

jfreesvg

debug	Enable debugging during compilation.

jna

awt	Enables support for Java AWT
nio-buffers	Enables support for NIO buffers

log4j

javamail	Build the SMTPAppender
jms	Build the JMSAppender

logback

tomcat	Builds Apache Tomcat support

lucene

contrib	Include extra functionality from contrib/

miglayout

swt	Add support for the SWT toolkit.

oracle-jdk-bin

commercial	Install features requiring a commercial license for production use
derby	Install bundled Derby (Java database)
gentoo-vm	Allow this JDK to be recognised by Gentoo (package manager, eselect, java-config, EXPERIMENTAL!)
gtk2	Enable GTK+ 2 support in JavaFX
gtk3	Enable GTK+ 3 support in JavaFX
headless-awt	Don't install the X backend for AWT, needed by some GUIs (used to be X flag)
javafx	Install JavaFX libraries
jce	Install Java Cryptographic Extension Unlimited Strength Jurisdiction Policy Files
source	Install JVM (and optionally JavaFX) sources
visualvm	Install VisualVM debugging tool

oracle-jre-bin

commercial	Install features requiring a commercial license for production use
gentoo-vm	Allow this JRE to be recognised by Gentoo (package manager, eselect, java-config, EXPERIMENTAL!)
gtk2	Enable GTK+ 2 support in JavaFX
gtk3	Enable GTK+ 3 support in JavaFX
headless-awt	Don't install the X backend for AWT, needed by some GUIs (used to be X flag)
javafx	Install JavaFX libraries
jce	Install Java Cryptographic Extension Unlimited Strength Jurisdiction Policy Files

proguard

ant	Ant task for using ProGuard in build.xml scripts
j2me	Adds support for J2ME Wireless Toolkit

protobuf-java

nano	Enable code generator and runtime library designed specifically for resource-constrained systems, like Android

rxtx

lfd	Installs and uses LockFileServer daemon (lfd)

sbt

binary	Install from (Gentoo-compiled) binary instead of building from sources. Set this when you run out of memory during build.

swt

webkit	Embedded browser support via net-libs/webkit-gtk:2, replacing former xulrunner-based browser.

dev-lang

bas

lr0	Use the LR0 parser instead of the recursive descending parser

crystal

blocking-stdio-hack	Keep STDIO file descriptors in blocking mode.
debug	Build each module as a separate object file. Speeds build up.
xml	Use the dev-libs/libxml2 library to enable Crystal xml module
yaml	Use the dev-libs/libyaml library to enable Crystal yaml module

ekopath

mpich	Include pre-built MPICH libraries
openmpi	Include pre-built OpenMPI 1.x libraries
openmpi2	Include pre-built OpenMPI 2.x libraries

erlang

compat-ethread	Enable compatibility with pre-pentium 4 CPUs in the ethread library.
dirty-schedulers	Enable dirty schedulers
halfword	Enable halfword emulator
hipe	HIgh Performance Erlang extension
kpoll	Enable kernel polling support

fpc

ide	Build and install the Free Pascal Compiler IDE

gdl

eigen	Build matrix manipulation with dev-cpp/eigen
grib	Add support for the meteorological GRIB format with sci-libs/grib_api
gshhs	Add support for projection adn continent maps with sci-geosciences/gshhs-data
hdf	Add support for the Hierarchical Data Format v.4
proj	Add support for sci-libs/proj (geographic projections)
udunits	Add support for manipulating units of physical quantities

ghc

binary	Install the binary version directly, rather than using it to build the source version.
ghcbootstrap	Internal: Bootstrap GHC from an existing GHC installation.
ghcmakebinary	Internal: Build binary friendly for redistribution.

gnat-gpl

awt	Useful only when building GCJ, this enables Abstract Window Toolkit (AWT) peer support on top of GTK+
cilk	Support the Cilk Plus language (C/C++ based languages for parallel programming)
fixed-point	Enable fixed-point arithmetic support for MIPS targets in gcc (Warning: significantly increases compile time!)
go	Build the GCC Go language frontend.
graphite	Add support for the framework for loop optimizations based on a polyhedral intermediate representation
libssp	Build SSP support into a dedicated library rather than use the code in the C library (DO NOT ENABLE THIS IF YOU DON'T KNOW WHAT IT DOES)
mpx	Enable support for Intel Memory Protection Extensions (MPX)
nopie	Disable PIE support (NOT FOR GENERAL USE)
nossp	Disable SSP support (NOT FOR GENERAL USE)
objc	Build support for the Objective C code language
objc++	Build support for the Objective C++ language
objc-gc	Build support for the Objective C code language Garbage Collector
pgo	Build GCC using Profile Guided Optimization (PGO)
regression-test	Run the testsuite and install the results (requires FEATURES=test)
sanitize	Build support for various sanitizer functions (ASAN/TSAN/etc...)
ssp	Build packages with stack smashing protector on by default
vtv	Build support for virtual table verification (a C++ hardening feature)

go

gccgo	Enable bootstrapping using gccgo

icon

iplsrc	install the icon programming library source

lazarus

minimal	Don't build extra packages from the bigide component

logtalk

fop	Support for generating pdf documentation using fop
xslt	Support for generating html documentation using xslt

lua

deprecated	make deprecated data structures/routines available

luajit

lua52compat	Enable some upwards-compatible features from Lua 5.2 that are unlikely to break existing code.

mercury

erlang	Support Mercury Erlang grade
trail	Support Mercury trail grades

mlton

binary	install a binary version (need to do this once to bootstrap, until smlnj is supported)

moarvm

asan	Enable clang's Address Sanitizer functionality. Expect longer compile time.
clang	Use clang compiler instead of GCC
jit	Enable Just-In-Time-Compiler. Has no effect except on AMD64 and Darwin.
optimize	Enable optimization via CFLAGS
ubsan	Enable clang's Undefined Behavior Sanitizer functionality. Expect longer compile time.

mono

pax_kernel	Enable if the user plans to run the package under a pax enabled hardened kernel
xen	Make mono generate code that is considerably faster on xen VMs but slightly slower on for normal systems.

nqp

clang	Toggle usage of the clang compiler in conjunction with MoarVM
moar	Build the MoarVM backend (experimental/broken)

ocaml

flambda	Enables the Flambda optimizer: A new intermediate representation (introduced in ocaml 4.03) in the depths of the compiler designed to allow for better inlining.
spacetime	Enables the Spacetime memory profiler. See https://caml.inria.fr/pub/docs/manual-ocaml/spacetime.html for more information.

orc

pax_kernel	Apply patch needed for pax enabled kernels.

perl

ithreads	Enable Perl threads, has some compatibility problems

php

argon2	Enable password hashing algorithm from app-crypt/argon2
cli	Enable CLI SAPI
coverage	Include gcov symbols for test coverage and lcov reports. Only useful for extension developers, and requires GCC.
embed	Enable embed SAPI
enchant	Add supports Enchant spelling library.
fileinfo	Add fileinfo extension support
filter	Add filter extension support
fpm	Enable the FastCGI Process Manager SAPI
gd	Adds support for gd (bundled with PHP)
hash	Enable the hash extension
intl	Enables the intl extension for extended internalization support
json	Enable JSON support
ldap-sasl	Add SASL support for the PHP LDAP extension
libmysqlclient	Use libmyslclient driver for mysql, mysqli, PDO_Mysql (not recommended)
lmdb	Enable support for dev-db/lmdb db backend
opcache	Enables built-in opcode cache, replacing pecl-apc et al.
pdo	Enable the bundled PDO extensions
phar	Enables the phar extension to provide phar archive support
phpdbg	Enable the PHP Debug Command Line SAPI (like gdb for php)
sodium	Enable support for crypto through libsodium
tokyocabinet	Enable support for dev-db/tokyocabinet db backend
vpx	Enable webp support for GD in php-5.x
webp	Enable webp support for GD in php-7.x
xmlreader	Enable XMLReader support
xmlwriter	Enable XMLWriter support
xslt	Enable the XSL extension
zip	Enable ZIP file support
zip-encryption	Enable ZIP file encryption from dev-libs/libzip

polyml

portable	Build the portable interpreter version of Poly/ML instead of native

python

threads	Enable threading support. (DON'T DISABLE THIS UNLESS YOU KNOW WHAT YOU'RE DOING)
wide-unicode	Enable wide Unicode implementation which uses 4-byte Unicode characters. Switching of this USE flag changes ABI of Python and requires reinstallation of many Python modules. (DON'T DISABLE THIS UNLESS YOU KNOW WHAT YOU'RE DOING)
wininst	Install Windows executables required to create an executable installer for MS Windows.

qu-prolog

pedro	Pedro subscription/notification communications system

rakudo

clang	Use Clang to compile the MoarVM backend
moar	Use the MoarVM as backend

rubinius

llvm	Build with llvm. Currently the package only builds against old versions of llvm.

ruby

jemalloc	Use dev-libs/jemalloc for memory allocation.
rdoc	Install dev-ruby/rdoc after installing Ruby.
readline	Use the sys-libs/readline library to provide the readline extension, used for instance by the irb tool. This flag is meaningful only if the libedit USE flag is disabled. If neither libedit nor readline USE flags are enabled, the readline extension will not be built (and irb will lose line editing functionality).
rubytests	Install ruby tests that can only be run after ruby is installed

rust

clang	Use sys-devel/clang for building
libcxx	Use sys-libs/libcxx as standard library when building with sys-devel/clang
system-llvm	Use system sys-devel/llvm in place of the bundled one

scala

binary	Install from (Gentoo-compiled) binary instead of building from sources. Set this when you run out of memory during build.

spidermonkey

custom-optimization	Build with user-specified compiler optimizations (-Os, -O0, -O1, -O2, -O3) from CFLAGS (unsupported)
debug	Enable assertions to allow for easier debugging of programs that link to spidermonkey -- note this will often crash software on regular end-user systems
system-icu	Use the system-wide dev-libs/icu instead of bundled -- note, only takes effect when icu flag is enabled
threadsafe	Build a threadsafe version of spidermonkey

swi-prolog

archive	Use libarchive for extension packs
uuid	Use ossp-uuid for UUID pack

swig

ccache	build ccache-swig(a fast compiler cache)

yap

R	Enable support for connecting R to Prolog

dev-libs

DirectFB

bmp	build BMP image provider
divine	enable DiVine
drmkms	build with DRM/KMS support
dynload	enable dynload support
egl	build with EGL support
fusiondale	enable FusionDale
fusionsound	enable FusionSound
gles2	build gles2 gfxdriver
imlib2	build Imlib2 image provider
input_hub	provides an asynchronous interface to the input devices available and those being added/removed
mpeg2	build MPEG2 image provider
mpeg3	build Libmpeg3 video provider
multicore	enable multicore support
pnm	build PNM (PBM/PGM/PPM) image provider
sawman	enable SaWMan (window manager and application manager)
swfdec	build Swfdec (Flash decoder) video provider
tremor	build Ogg/Vorbis music provider using Tremor
webp	build WebP image provider

ace

ciao	Include Component Intergraced Ace ORB into the build of ace
tao	Include the ACE ORB (CORBA stuff) (called tao) into the build of ace

actor-framework

benchmarks	Due to the number of out-of-tree deps, these only get installed as docs
boost	Make use of Boost's ASIO functionality
cash	Build the C Actor Shell for introspection and debugging
debug	Raises log-level to DEBUG, enables runtime checks and address sanitizer
doc	Compiles and installs the documentation as PDF and HTML
examples	Installs the provided example source files
mem_management	Enables built-in memory management
nexus	Nexus is the central component for CAF's runtime inspection
opencl	Compiles against the provided opencl implementation
riac	Runtime inspection and configuration
static	Provides a static build
test	Builds the provided unit tests

antlr-c

debugger	Compiles debug info into the library

appstream

apt	Enables Debians APT support

appstream-glib

stemmer	Add word stemming via dev-libs/snowball-stemmer.

apr

older-kernels-compatibility	Enable binary compatibility with older kernels
urandom	Use /dev/urandom instead of /dev/random

apr-util

libressl	Use dev-libs/libressl instead of dev-libs/openssl for 'openssl' USE flag
nss	Install apr_crypto_nss module
openssl	Install apr_crypto_openssl module

beignet

ocl-icd	Enable compatibility with the dev-libs/ocl-icd OpenCL ICD loader
ocl20	Enable experimental OpenCL 2.0 support on Skylake and newer architectures

bitset

jemalloc	Use dev-libs/jemalloc for allocations
tcmalloc	Use tcmalloc from dev-util/google-perftools for allocations

blitz

boost	Enable usage of boost::serialization

boost

context	Build and install the Boost.Context (and Boost.Fiber) library and all other Boost libraries that depend on it
debug	Build and install only the debug version of the Boost libraries. Only enable this flag if you're developing against boost.
doc	Install the full API documentation documentation. This takes over 200MB of extra disk space.
nls	Build libboost_locale. This library requires compatible C library interfaces, which might not be provided by uClibc or other embedded libraries.
threads	Build multi-thread-compatible libraries instead of single-threaded only.
tools	Build and install the boost tools (bcp, quickbook, inspect, wave)

botan

boost	use dev-libs/boost

c-blosc

lz4	Enable lz4 compression
snappy	Enable snappy compression
zstd	Enable zstd compression

check

subunit	Enable support for the subunit unit test protocol

cyberjack

fox	Enable installation of x11-libs/fox based fxcyberjack program

cyrus-sasl

authdaemond	Add Courier-IMAP authdaemond unix socket support (net-mail/courier-imap, mail-mta/courier)
ldapdb	Enable ldapdb plugin
openldap	Add ldap support for saslauthd
sample	Enable sample client and server
srp	Enable SRP authentication
urandom	Use /dev/urandom instead of /dev/random

dbus-c++

ecore	Use Ecore integration
glib	Use glib integration

eekboard

libcanberra	Enable support for media-libs/libcanberra
xtest	Enable support for x11-libs/libXtst

efl

bmp	Enable WBMP image loader
drm	Enable DRM engine
eet	Enable Eet image loader
egl	Enable EGL rendering
fribidi	Enable bidirectional text support
gles	Enable the OpenGL ES GL implementation
glib	Enable dev-libs/glib support
harfbuzz	Enable complex text shaping and layout support
ibus	Enable Intelligent Input Bus
ico	Enable Ico image loader
oldlua	USE dev-lang/lua instead of dev-lang/luajit
physics	Enable Bullet physics effects and support
pixman	Enable PixMan for software rendering
ppm	Enable PMAPS image loader
psd	Enable PSD image loader
scim	Enable Smart Common Input Method
tga	Enable Tga image loader
tslib	Enable x11-libs/tslib for touchscreen events
unwind	Enable debug support via sys-libs/libunwind
valgrind	Enable usage of dev-util/valgrind in debug
webp	Enable WebP image loader
xim	Enable X Input Method

elfutils

lzma	Support automatic decompression of LZMA-compressed files and kernel images
threads	Build the libraries with thread safe support
utils	Install command-line utilities (all the eu-* programs)

fcgi

html	Install HTML documentation

folks

telepathy	Load contacts from the Telepathy framework
tracker	Load contacts from app-misc/tracker index
utils	Build the folks-inspect utility
zeitgeist	Add support for Zeitgeist event tracking system

fstrm

utils	Build fstrm utility programs

gecode

gist	Enable Gist, the Gecode Interactive Search Tool
gmp	Enable trigonometric and transcendental float constraints

gf2x

bindist	Disable automatic fine-tuning to local processor features like pclmul or sse2.
custom-tune	Extra long compile time for tuning hardware specific low-level routines
fft	Build an FFT API for multiplication of 2 polynomials over GF(2)

glib

dbus	Enable dependencies required by glib libraries using dbus service to manage settings saving
mime	Pull in shared MIME database that many glib-based applications require at runtime to detect or open files. Warning: do not disable this flag unless installing on a headless server.
systemtap	Build support for profiling and tracing using dev-util/systemtap
utils	Install gtester-report utility to generate test report files for your software; build gresource utility with ELF support.

gmime

smime	Enable experimental S/MIME support

gmp

asm	Enable use of hand optimized assembly routines (faster execution)
pgo	After building gmp, run some tests against to produce faster libraries -- this option will double the compile time

gobject-introspection

doctool	Install g-ir-doc-tool for generating documentation from introspected data

hidapi

fox	Build a x11-libs/fox GUI

input-pad

eekboard	Enable support for dev-libs/eekboard
xtest	Enable support for x11-libs/libXtst

intel-common

compiler	Install the libraries needed for the icc and ifort compilers

jemalloc

hugepages	Enable transparent huge page support
lazy-lock	Enable lazy locking (only lock when multi-threaded)
stats	Enable statistics calculation/reporting
xmalloc	Add support for xmalloc (abort-on-out-of-memory)

kreport

marble	Enable displaying of maps using kde-apps/marble
scripting	Support Qml scripting using dev-qt/qtdeclarative

leveldb

snappy	support the snappy compression library

libbase58

tools	Build command line base58 tool

libburn

cdio	Enable EXPERIMENTAL use of libcdio as system adapter
track-src-odirect	Read track input with O_DIRECT (see man 2 open), this may deliver a better write performance in some situations

libcdio

minimal	Only build the libcdio library and little more, just to be used to link against from multimedia players. With this USE flag enabled, none of the command-line utilities are built, nor is the CDDA library.

libcec

cubox	Enable support for enable support for the TDA995x
exynos	Enable support for Exynos chipsets
raspberry-pi	Enable support for the Raspberry Pi
xrandr	Enable detection of active HDMI using xrandr extensions

libcgroup

daemon	Install the configuration tools and init/config files.
tools	Install the cgroup rules processing daemon and init/config files.

libclsync

extra-debug	Enable extra debugging. This will hurt performance badly. Be ready for tons of output.
extra-hardened	Enable extra security checks. This may hurt performance.

libdbusmenu

gtk	Enable support for GTK+2
gtk3	Enable support for GTK+3

libdivecomputer

tools	Install tools that can be used to test the library.

libdynd

cuda	Enable NVIDIA CUDA toolkit support
mkl	Enable a plugin for Intel Math Kernel Library sci-libs/mkl

libevent

debug	Support runtime debug mode and malloc hooks (for programmers)

libffi

pax_kernel	Use PaX emulated trampolines, for we can't use PROT_EXEC

libflatarray

cuda	Enables plugins for NVIDIA GPUs (e.g. CUDAAllocator)

libgdata

gnome-online-accounts	Enable net-libs/gnome-online-accounts support

libgit2

gssapi	Enable GSSAPI support for SPNEGO auth
ssh	Enable SSH transport support
trace	Enable tracing support

libgit2-glib

ssh	Enable SSH transport support

libgpg-error

common-lisp	Install common-lisp files

libgpuarray

cuda	Enable NVIDIA CUDA toolkit support
opencl	Enable OpenCL support

libgweather

glade	Installs catalog files for dev-util/glade

libical

glib	Enable dev-libs/glib GObject interface support

libisoburn

cdio	Enable EXPERIMENTAL use of libcdio as system adapter
external-filters	Allow the use of external processes as file content filters (Note: this is a potential security risk)
external-filters-setuid	Also allow the use of external setuid processes as file content filters (Note: this is a potential security risk)
frontend-optional	Use dev-tcltk/bwidget which is not strictly required for the frontend
launch-frontend	Enable the tcl gui for xorriso
launch-frontend-setuid	Enable the tcl gui for xorriso under setuid

libisofs

verbose-debug	Enable verbose debug messages

liblogging

rfc3195	Enables RFC 3195 protocol (aka syslog-reliable) support. If you don't know what this is, you don't need it!
stdlog	Enables liblogging's core component (think of it as a the next version of the syslog(3) API).

libmail

apop	Enables the APOP authentication method

libmateweather

gtk3	Build with GTK+3 instead of GTK+2

libmemcached

hsieh	Use Hsieh hash algorithm.
libevent	Use the libevent event loop interface.
sasl	Use sasl auth for communications.

libmspack

utils	Enables building cabrip, chmextract, msexpand and oabextract

libnfc

pcsc-lite	Enable NFC drivers that require pcsc-lite

libnl

doc	Install development documentation
python	Install experimental dev-lang/python bindings
utils	Install command line interface utils

liborcus

spreadsheet-model	Enable the spreadsheet model implementation
tools	Build various low-level parsers

libowfat

diet	Compile against dev-libs/dietlibc

libp11

doc	Generate and install API documentation for the package.

libpcre

bzip2	Add support for pcregrep command to search within bzip2-compressed files (via app-arch/bzip2).
pcre16	Build PCRE library for 16 bit characters (e.g. UTF-16).
pcre32	Build PCRE library for 32 bit characters (e.g. UTF-32).
readline	Add support for command line editing to pcretest, through sys-libs/readline.
recursion-limit	Limit match recursion to 8192; if disabled, the default limit is used, which is the same as the match limit.
zlib	Add support for pcregrep command to search within gzip-compressed files (via sys-libs/zlib).

libpcre2

bzip2	Add support for pcregrep command to search within bzip2-compressed files (via app-arch/bzip2).
pcre16	Build PCRE library for 16 bit characters (e.g. UTF-16).
pcre32	Build PCRE library for 32 bit characters (e.g. UTF-32).
readline	Add support for command line editing to pcretest, through sys-libs/readline.
recursion-limit	Limit match recursion to 8192; if disabled, the default limit is used, which is the same as the match limit.
zlib	Add support for pcregrep command to search within gzip-compressed files (via sys-libs/zlib).

libpeas

glade	Install the glade catalog
python	Build support for loading dev-lang/python plugins

librdkafka

lz4	Enable support for Kafka's LZ4 compression based on KIP-57 (uses app-arch/lz4)

libressl

asm	Enables assembly

libsecp256k1

asm	Enable x86_64 assembly optimisation
ecdh	Enable ECDH shared secret computation
endomorphism	Enable endomorphism
experimental	Allow experimental USE flags
recovery	Enable ECDSA pubkey recovery module
schnorr	Enable Schnorr signature module
test_openssl	Enable OpenSSL comparison tests

libslz

tools	Install additional tools (zenc, zdec)

libsodium

asm	Enables assembly implementations
urandom	Use /dev/urandom instead of /dev/random

libsolv

rpm	Enable support for RPM files

libspt

libtirpc	Build against net-libs/libtirpc for RPC support

libsqlora8

orathreads	Use Oracle threads

libtasn1

valgrind	Enable usage of dev-util/valgrind in debug

libtermkey

demos	Install demos, which pulls in dev-libs/glib

libucl

regex	Enable regex checking for schema
signatures	Enable signatures check
urlfetch	Enable URLs fetch
utils	Install the chargen and objdump utilities

libunibreak

doc	Install html API documentation.
man	Generate man pages with doxygen.

libverto

glib	Support event loops using dev-libs/glib
libev	Support event loops using dev-libs/libev
libevent	Support event loops using dev-libs/libevent
tevent	Support event loops using sys-libs/tevent

libzia

ftdi	Enable support for FTDI USB chips

link-grammar

aspell	Adds support for app-text/aspell spell checker
hunspell	Adds support for app-text/hunspell spell checker

log4cplus

iconv	Use inconv for wchar_t <-> char conversions. See also log4cplus's unicode.txt documentation
working-c-locale	Use the C99 locale facilities for wchar_t <-> char conversions. See also log4cplus's unicode.txt documentation
working-locale	Use C++'s std::locale for wchar_t <-> char conversions. See also log4cplus's unicode.txt documentation

log4cxx

smtp	Offer SMTP support via net-libs/libesmtp

m17n-lib

X	Build the Graphical User Interface API and utilities
anthy	Enable support for app-i18n/anthy input method
athena	Enable the MIT Athena widget set (x11-libs/libXaw)
gd	Build API and utilities based on media-libs/gd. This flag is only meaningful if the X USE flag is also enabled.
libotf	Use dev-libs/libotf to handle OpenType fonts
libxml2	Use dev-libs/libxml2 to parse XML

nss

cacert	Include root/class3 certs from CAcert (http://www.cacert.org/)
nss-pem	Add support for libnsspem
utils	Install utilities included with the library

onigmo

combination-explosion-check	enable combination explosion check
crnl-as-line-terminator	enable CR+NL as line terminator

oniguruma

combination-explosion-check	enable combination explosion check
crnl-as-line-terminator	enable CR+NL as line terminator

opencryptoki

tpm	Enable support for Trusted Platform Module (TPM) using app-crypt/trousers

openct

debug	Add debug output to the driver library for pcsc-lite.
pcsc-lite	Build a driver library for sys-apps/pcsc-lite, providing PC/SC API access to devices supported by OpenCT.
udev	Install rules for sys-fs/udev to auto-start openct.

openobex

irda	Enable IrDA support

opensc

ctapi	Use CT-API for accessing Smartcard hardware
openct	Use dev-libs/openct (and CT-API) for accessing Smartcard hardware
pcsc-lite	Use sys-apps/pcsc-lite (and PC/SC API) for accessing Smartcard hardware
secure-messaging	Enable secure messaging

openssl

asm	Support assembly hand optimized crypto functions (i.e. faster run time)
bindist	Disable/Restrict EC algorithms (as they seem to be patented) -- note: changes the ABI
rfc3779	Enable support for RFC 3779 (X.509 Extensions for IP Addresses and AS Identifiers)
sslv2	Support for the old/insecure SSLv2 protocol -- note: not required for TLS/https
sslv3	Support for the old/insecure SSLv3 protocol -- note: not required for TLS/https
tls-heartbeat	Enable the Heartbeat Extension in TLS and DTLS

pkcs11-helper

nss	Enable NSS crypto engine

poco

7z	Add Support for the 7z archive format
apache	Enable support to write Apache modules using POCO
cppparser	Build and install a minimal C++ parser
crypto	Encryption and digital signing classes
data	Database abstraction layer to easily send/retrieve data to/from various databases
file2pagecompiler	Utility to convert ordinary files to Page Compiler source files
json	Add JSON support
mongodb	Add dev-db/mongodb support
net	Classes to write network clients & servers
pagecompiler	Simple compiler translating HTML pages containing embedded C++ code into HTTPRequestHandler classes
pocodoc	POCO documentation generator
util	Several utility classes (like logger, timer, config file parser)
zip	Add support for the zip & gz archive formats

ppl

lpsol	Build the ppl_lpsol linear programming problem solver

protobuf

java	Builds the Java implementation. This is not needed for Java support in protoc.
python	Builds the Python implementation. This is not needed for Python support in protoc.

purpose

kaccounts	Enable support for system-wide defined KAccounts

softhsm

migration-tool	Build db migration tool

starpu

cuda	Enable NVIDIA CUDA toolkit support
gcc-plugin	Enable GCC extension plugin (experimental)
opencl	Enable OpenCL support

sway

gdk-pixbuf	Enable additional image format support via the x11-libs/gdk-pixbuf library.
swaybar	Build 'swaybar': sway's status bar component.
swaybg	Build 'swaybg': allows to set a desktop background image.
swaygrab	Build 'swaygrab': allows taking screenshots or screencasts.
swaylock	Build 'swaylock': sway's screen locker.
swaymsg	Build 'swaymsg': tool for communicating with a running sway instance.
tray	Enable support for StatusNotifierItem tray specification.
wallpapers	Install sway's default wallpaper image.

tinyxml

stl	Compile with TIXML_USE_STL support

tntnet

server	Enable tntnet server daemon

totem-pl-parser

archive	Enables support for accessing media files in archives transparently via app-arch/libarchive
quvi	Use media-libs/libquvi for parsing video links

tvision

gpm	Support text mode mouse through sys-libs/gpm

ucommon

socks	Build with socks proxy support

userspace-rcu

regression-test	Run regression tests (requires FEATURES=test)

ustr

ustr-import	Install ustr-import developer program and source code for bundling.

weston

colord	Allow setting color managment
drm	Enable drm compositor support
editor	Install wayland-editor example application
fbdev	Enable fbdev compositor support
gles2	Use GLESv2 cairo instead of full GL
headless	Headless backend and a noop renderer, mainly for testing purposes
ivi	Enable the IVI shell
launch	Install weston-launch utility
rdp	Enable Remote Desktop Protocol compositor support
resize-optimization	Increase performance, allocate more RAM. Recommended to disable on Raspberry Pi
rpi	Raspberry Pi GPU support
screen-sharing	Enable screen-sharing through RDP
unwind	Enable libunwind usage for backtraces
wayland-compositor	Enable Wayland compositor support
webp	Add support for the WebP image format
xwayland	Enable ability support native X11 applications

wlc

X	Enable X11 backend.
systemd	Enable support for systemd-logind.
xwayland	Enable XWayland application support.

xapian

brass	Enabled brass backend db support
chert	Enabled chert backend db support
glass	Enabled glass backend db support
inmemory	Enabled inmemory backend db support

xerces-c

iconv	Use iconv (virtual/libiconv) as message loader and transcoder (in general it would be possible to use iconv only as message loader and something else like icu or the native method as transcoder and vice-versa, but this is a less common case and hard to handle)
threads	Enable threading support through pthread (or other libraries on AIX, IRIX, HPUX, Solars). Highly recommended

xml-security-c

nss	Use dev-libs/nss for certain crypto operations (configureable at runtime)
xalan	Enable support for XSLT and XPath parsing by dev-libs/xalan-c

xmlrpc-c

abyss	Build the Abyss mini web-server.
libxml2	Use dev-libs/libxml2 to parse XML instead of the internal expat library.
threads	Controls whether to build the Abyss web-server with pthreads or fork 'threading'.
tools	Build the xmlrpc* tools.

xmlsec

gcrypt	Install xmlsec-gcrypt library
gnutls	Install xmlsec-gnutls library
nss	Install xmlsec-nss library
openssl	Install xmlsec-openssl library

xqilla

faxpp	Use dev-libs/faxpp instead of Xerces-C for certain tasks
htmltidy	Use app-text/htmltidy when parsing HTML

yaz

ziffy	Install ziffy, a promiscuous Z39.50 APDU sniffer

dev-lisp

abcl

clisp	Build Armed Bear Common Lisp using GNU CLISP
cmucl	Build Armed Bear Common Lisp using CMU Common Lisp
jad	Enable support for disassembling compiled code using JAD

clisp

hyperspec	Use local hyperspec instead of online version
new-clx	Build CLISP with support for the NEW-CLX module which is a C binding to the Xorg libraries
pari	Build CLISP with support for the PARI Computer Algebra System
svm	Build CLISP with support for the Support Vector Machine module

clx

doc	Builds documentation

cmucl

source	Include source code for CMUCL in installation

ecls

gengc	Use generational garbage collection (experimental)
libatomic	Use dev-libs/libatomic_ops library
precisegc	Use type information during garbage collection (experimental)

gcl

ansi	Build a GCL with ANSI support (else build a traditional CLtL1 image)
athena	Build xgcl - an interface to x11-libs/libXaw

sbcl

pax_kernel	Enable if the user plans to run the package under a pax enabled hardened kernel

dev-lua

lpeg

luajit	Use dev-lang/luajit instead of dev-lang/lua

lua-openssl

luajit	Use dev-lang/luajit instead of dev-lang/lua

luacheck

luajit	Use dev-lang/luajit instead of dev-lang/lua

luafilesystem

luajit	Use dev-lang/luajit instead of dev-lang/lua

luaossl

luajit	Use dev-lang/luajit instead of dev-lang/lua

luarocks

curl	Uses net-misc/curl for fetching lua packages instead of net-misc/wget.
openssl	Uses dev-libs/openssl for verifying lua packages instead of md5sum.

luassert

luajit	Use dev-lang/luajit instead of dev-lang/lua

luvit

bundled-libs	Use bundled versions of some libraries.

messagepack

luajit	Use the lua just-in-time compiler dev-lang/luajit instead of dev-lang/lua

mpack

luajit	Use dev-lang/luajit instead of dev-lang/lua

say

luajit	Use dev-lang/luajit instead of dev-lang/lua

dev-ml

cairo-ocaml

pango	Enable support for x11-libs/pango

csv

lwt	Enables the Lwt-based library for asynchronous operations.

dose3

parmap	Adds multi-core CPU support via dev-ml/parmap.
rpm4	Adds support for handling rpm4 files.
zip	Adds support for handling zip files.

eliom

ppx	Enable PPX syntax extension support.

js_of_ocaml

camlp4	Build with camlp4 syntax extensions.
deriving	Enable dev-ml/deriving support for improving the type safety.
lwt	Enable dev-ml/lwt support.
ppx	Enables the ppx syntax extension
react	Enable functionnal reactive programming support.

lablgtk

glade	Enable libglade bindings compilation.
gnomecanvas	Enable libgnomecanvas bindings compilation.
sourceview	Enable GtkSourceView support

logs

cli	Enables the Logs_cli library that provides command line support for controlling Logs.
fmt	Enables the Logs_fmt reporter.
lwt	Enables the Logs_lwt library that provides Lwt logging functions.

lwt

camlp4	Enable camlp4 syntax extension
libev	Enable the dev-libs/libev-based backend.
ppx	Enables the ppx syntax extension

ocaml-cohttp

async	Enables support for the dev-ml/async asynchronous execution library.
lwt	Enables support for the dev-ml/lwt cooperative light-weight thread library.

ocaml-cstruct

async	Support for asynchronous execution
lwt	Enable threads via lwt
ppx	Enable the ppx syntax extension

ocaml-websocket

async	Enables support for the dev-ml/async asynchronous execution library.
lwt	Enables support for the dev-ml/lwt cooperative light-weight thread library.

ocamlnet

httpd	Enables net-httpd web server component
zip	Enables netzip support to read/write gzip data using object channels

onanomsg

lwt	Enables lwt support.

pgocaml

camlp4	Enable PG'Ocaml syntax extension.

tyxml

camlp4	Enables the camlp4 syntax extension (deprecated)
ppx	Enables the ppx syntax extension (preferred)

uutf

utftrip	Builds and install the utftrip executable: Among other things, reads unicode on stdin and rewrites it on stdout.

zarith

mpir	Use MPIR library instead of GMP.

dev-perl

App-Nopaste

browser	Spawn browser with pasted page
clipboard	copying of URLs with -x/--copy
github	Github authentication
pastebin	pastebin.com support

Business-ISBN

barcode	Install dev-perl/GD-Barcode for rendering ISBN numbers as barcodes
xisbn	Install dev-perl/Mojolicious for querying xisbn.worldcat.org

Config-Any

conf	Install dev-perl/Config-General to support decoding .conf/.cnf files
ini	Install dev-perl/Config-Tiny to support decoding INI config files
json	Install support libraries to support decoding JSON config files
xml	Install support libraries to support decoding XML config files
yaml	Install support libraries to support decoding YAML config files

Convert-UUlib

system-uulib	Use dev-libs/uulib instead of bundled version.

Cookie-Baker

xs	Install dev-perl/Cookie-Baker-XS for accelerated performance

Coro

ev	Build support for using dev-perl/EV as an event-loop via Coro::EV
event	Build support for using dev-perl/Event as an event-loop via Coro::Event

DBD-SQLite

system-sqlite	Use the system-wide dev-db/sqlite installation

DBD-mysql

embedded	Support embedded server (libmysqld)
ssl	Compile in support for SSL connections via libmysqlclient

DBIx-Class

admin	Modules required for the DBIx::Class administrative library
admin_script	Modules required for the CLI DBIx::Class interface dbicadmin
deploy	Modules required for "deploy" in DBIx::Class::Storage::DBI and "deploymen_statements" in DBIx::Class::Storage::DBI
replicated	Modules required for DBIx::Class::Storage::DBI::Replicated

File-HomeDir

xdg	Ensure XDG Semantics for returned paths via x11-misc/xdg-user-dirs

File-Which

pwhich	Install dev-perl/App-pwhich which used to be a part of this package

GD

animgif	Enable animated gif support
fcgi	Build for FastCGI compatibility via dev-libs/fcgi instead of using PerlIO

Graphics-ColorNames

recommended	Install recommended support modules

HTML-Mason

modperl	Enable www-apache/mod_perl support

HTTP-Entity-Parser

xs	Install C-Based dependieces for faster performance

JSON

xs	Install C-based dev-perl/JSON-XS for faster performance

JSON-MaybeXS

xs	Install a C-Based backend to make JSON encode/decode fast

Lab-VXI11

libtirpc	Build against net-libs/libtirpc for RPC support

List-MoreUtils

xs	Install C-Based backend implementation for performance

MCE

sereal	Install dev-perl/Sereal-Encoder and decoder for faster worker IPC

Mail-IMAPClient

md5	Install support for DIGEST-MD5 and CRAM-MD5 Authentication
ntlm	Install support for NTLM Authentication
ssl	Install support for SSL Connections
zlib	Install support for COMPRESS DEFLATE connections

Net-OpenSSH

sftp	Enable SFTP protocol support.

Net-SSH2

gcrypt	Use libgcrypt instead of openssl

PDL

badval	Enable bad values support
hdf	Enable HDF (version 4) format support
netpbm	Enable NETPBM and MPEG support
pdl2	Build pdf2 shell (requires Devel-REPL)
pgplot	Enable PGPLOT plotting capabilities

Panotools-Script

gui	Installs GUIs for some tools

Ref-Util

xs	Install C-Based dev-perl/Ref-Util-XS for accelerated performance

Sub-Name

suggested	Install extra dependencies needed for extended regression tests

Sysadm-Install

hammer	Enable hammer() funtion to run a command in the shell and simulate a user hammering the ENTER key to accept defaults on prompts

Test-Warnings

suggested	Install optional dependencies for extra tests

Text-CSV

xs	Install dev-perl/Text-CSV_XS for accelerated decoding

WWW-Form-UrlEncoded

xs	Install C-Based dependieces for faster performance

perl-headers

debug	Add source locations in generated .ph files to assist with debugging when errors occur
sizeof-warning	Include logic to warn when a .ph file tries to use a sizeof() that is unknown

dev-php

PEAR-HTTP_Request2

curl	Force dev-lang/php to be compiled with curl extension
fileinfo	Force dev-lang/php to be compiled with fileinfo extension
ssl	Force dev-lang/php to be compiled with ssl extension
zlib	Force dev-lang/php to be compiled with zlib extension

PEAR-PHP_Beautifier

cli	Require dev-lang/php to be built with the "cli" SAPI and install the php_beautifier script.

ZendFramework

cli	Enables the CLI
doc	Installs the documentation
examples	Installs the examples
minimal	Installs the minimal version without Dojo toolkit, tests and demos

agavi

executable	Install the "agavi" executable used to manage projects. This requires dev-php/phing, and may be omitted if you are (for example) deploying an existing site to a production server.

maxmind-db-reader

extension	Build the C extension that uses dev-libs/libmaxminddb

pecl-apcu

lock_pthreadmutex	Enable pthread mutex locking
lock_pthreadrw	Enable pthread read/write locking
lock_semaphore	Enable semaphore locks instead of fcntl
lock_spinlock	Enable spin locks (EXPERIMENTAL)

pecl-event

extra	Add support of the Libevent extra API

pecl-memcached

igbinary	Enable support for the igbinary serializer
json	Enable support for json serialization

pecl-mysqlnd_qc

memcached	Use dev-libs/libmemcached as a storage handler
sqlite	Use dev-db/sqlite as a storage handler

pecl-redis

igbinary	Enables igbinary serialisation support

pecl-zmq

czmq	Use the czmq high level bindings

phing

zip	Support zip archives by requiring said support in dev-lang/php.

twig

extension	Build the C extension (only for php-5.6.x).

xcache

coverage	Enable the coverager module (not recommended for production servers).

dev-python

Kivy

camera	Install libraries needed to support camera
garden	Install garden tool to manage user maintained widgets

PyFoam

extras	Enable optional dependencies

PyQt4

X	Build bindings for the QtGui module
compat	Install the deprecated pyqtconfig module for backward compatibility
dbus	Build bindings for the QtDBus module
declarative	Build bindings for the QtDeclarative module
designer	Build bindings for the QtDesigner module and enable the designer plugin
help	Build bindings for the QtHelp module
multimedia	Build bindings for the QtMultimedia module
opengl	Build bindings for the QtOpenGL module
phonon	Build bindings for the phonon module
script	Build bindings for the QtScript module
scripttools	Build bindings for the QtScriptTools module
sql	Build bindings for the QtSql module
svg	Build bindings for the QtSvg module
testlib	Build bindings for the QtTest module
webkit	Build bindings for the QtWebKit module
xmlpatterns	Build bindings for the QtXmlPatterns module

PyQt5

bluetooth	Build bindings for the QtBluetooth module
dbus	Build bindings for the QtDBus module
declarative	Build bindings for the QtQml/QtQuick modules and enable the qmlscene plugin
designer	Build bindings for the QtDesigner module and enable the designer plugin
gles2	Use GLES 2.0 or later instead of full OpenGL
gui	Build bindings for the QtGui module
help	Build bindings for the QtHelp module
location	Build bindings for the QtLocation module
multimedia	Build bindings for the QtMultimedia module
network	Build bindings for the QtNetwork module
opengl	Build bindings for the QtOpenGL module
positioning	Build bindings for the QtPositioning module
printsupport	Build bindings for the QtPrintSupport module
sensors	Build bindings for the QtSensors module
serialport	Build bindings for the QtSerialPort module
sql	Build bindings for the QtSql module
svg	Build bindings for the QtSvg module
testlib	Build bindings for the QtTest module
webchannel	Build bindings for the QtWebChannel module
webengine	Build bindings for the QtWebEngine module
webkit	Build bindings for the QtWebKit module
websockets	Build bindings for the QtWebSockets module
widgets	Build bindings for the QtWidgets module
x11extras	Build bindings for the QtX11Extras module
xmlpatterns	Build bindings for the QtXmlPatterns module

PythonQt

extensions	Install extensions

QtPy

designer	Build bindings for the QtDesigner module and enable the designer plugin
gui	Build bindings for the QtGui module
pyqt5	Enable the dev-python/PyQt5 backend
pyside	Enable the dev-python/pyside backend
svg	Build bindings for the QtSvg module
testlib	Build bindings for the QtTest module
webkit	Build bindings for the QtWebKit module

amqplib

extras	Install extra tools to generate initial Python mod from an AMQP XML file

anyvc

bazaar	Add support for Bazaar
mercurial	Add support for Mercurial

celery

redis	Enables redis support
sqs	Enables Amazon SQS transport module for celery
yaml	Enable support of yaml as a configuration file format
zeromq	Enable logging and deployment via ZeroMQ

cgkit

3ds	Enable support for importing 3D Studio models

cvxopt

dsdp	Use interior point library sci-libs/dsdp
glpk	Use GNU Linear Programming Kit sci-mathematics/glpk

dap

server	Enable OpenDAP server support

dask

distributed	Add support for distributed computing with dev-python/distributed

django-cms

admin-style	Install plugin customizing admin panel styles
ckeditor	Install text-ckeditor plugin for rich text editing
file	Install djangocms file plugin
flash	Install djangocms flash plugin
inherit	Install djangocms inherit plugin
link	Install djangocms link plugin
picture	Install djangocms picture plugin
snippet	Install djangocms snippet plugin
teaser	Install djangocms teaser plugin
video	Install djangocms video plugin

django-tastypie

bip	An optional serialiser dev-python/biplist
digest	Library to aid in implementing HTTP Digest Authentication
lxml	An optional serialiser dev-python/lxml
yaml	An optional serialiser dev-python/yaml

django-two-factor-auth

yubikey	Adds support for Yubikeys via django-otp-yubikey

editorconfig-core-py

cli	Install command line interface as well as python library

falcon

cython	Build cython-based python modules

fastparquet

brotli	Enable support for brotli compression
snappy	Enable support for snappy compression

flask-restful

paging	Enable resource paging support

geopy

timezone	Enables localized date support
yahoo	Enables use of YahooPlaceFinder

glance_store

cinder	adds cinder backend support

gmpy

mpir	Use sci-libs/mpir as gmp implementation

icalendar

doc	Generate examples and other extra documentation

ipython

matplotlib	Add support for dev-python/matplotlib
mongodb	Enable support for MongoDB via dev-python/pymongo
nbconvert	Enable support for converting notebooks to various formats using app-text/pandoc
notebook	Install requirements for the web notebook based on www-servers/tornado
octave	Enable octave bridge via dev-python/oct2py

jira

filemagic	Include filemagic support (for identifying uploaded filetypes)
ipython	Include Interactive Python (IPython)
oauth	Support OAuth authentication

kaa-base

tls	SSL/TLS support via dev-python/tlslite

kafka-python

snappy	Install snappy compression/decompression support

kazoo

gevent	Enable support for the gevent based handler

kombu

amqplib	Enable amqplib support
msgpack	Enables MessagePack (de)serializer for Python
sqs	Enables Amazon SQS transport module for Kombu

markdown

pygments	Enable fancy pygments support

matplotlib

excel	Pull dev-python/xlwt for the exceltools toolkit
gtk2	Enable x11-libs/gtk+:2 support
gtk3	Enable x11-libs/gtk+:3 support
pyside	Qt support via dev-python/pyside

mpmath

matplotlib	Add support for dev-python/matplotlib

nbdime

webtools	Install web-based diff and merge tools.

netaddr

cli	Enable netaddr shell with dev-python/ipython

nltk

numpy	Use numpy for the saved word tokenizer

numexpr

mkl	Enable support for Intel Vector Math Library, part of sci-libs/mkl.

pandas

R	Enable support for R via dev-python/rpy
excel	Pull a few Python packages for Microsoft Excel i/o
full-support	Pull all packages to give pandas full support
html	Enable HTML i/o via dev-python/beautifulsoup

passlib

bcrypt	bcrpyt hash algoryptm support
scrypt	accelerated scrypt algoythm support
totp	time based one time password support

paste

flup	enable support for flup (and therefore for various wgsi servers and middleware)
openid	enable OpenID support

pillow

imagequant	Build with Image Quantization Library support

py-amqp

extras	Install extra tools to generate initial Python mod from an AMQP XML file

pygame

midi	Enable midi support using media-libs/portmidi

pygpu

cuda	Enable NVIDIA CUDA toolkit support
opencl	Enable OpenCL support

pyhamcrest

numpy	Enable optional dependence on dev-python/numpy

pyilmbase

numpy	Add bindings for dev-python/numpy use.

pyocr

cuneiform	Enable support for the app-text/cuneiform OCR engine
tesseract	Enable support for the app-text/tesseract OCR engine

pypax

ptpax	Enable PT_PAX_FLAGS support.
xtpax	Enable XATTR_PAX_FLAGS support.

pyplusplus

indexing	Install indexing_suite_v2 to enhance boost python
numpy	Generate code for dev-libs/boost-numpy to accelerate arrays

pypy

low-memory	Build using PyPy with the engine configured towards low memory footprint. This makes it possible to build PyPy using ~3.5G of RAM on amd64 and ~half of that on x86, at the cost of lengthened build time.
sandbox	Enable sandboxing functionality

pypy3

low-memory	Build using PyPy with the engine configured towards low memory footprint. This makes it possible to build PyPy using ~3.5G of RAM on amd64 and ~half of that on x86, at the cost of lengthened build time.
sandbox	Enable sandboxing functionality

pyside

X	Build QtGui and QtTest modules
declarative	Build QtDeclarative module
designer	Build QtDesigner and QtUiTools modules
help	Build QtHelp module
multimedia	Build QtMultimedia module
opengl	Build QtOpenGL module
phonon	Build phonon module
script	Build QtScript module
scripttools	Build QtScriptTools module
sql	Build QtSql module
svg	Build QtSvg module
webkit	Build QtWebKit module
xmlpatterns	Build QtXmlPatterns module

python-caja

gtk3	Build with GTK+3 instead of GTK+2

python-stdnum

vies	Enable VIES

pyudev

pygobject	Install PyGobject bindings
pyside	Install PySide bindings
qt4	Install PyQt4 bindings
qt5	Install PyQt5 bindings

pyyaml

libyaml	enable support for C implementation using libyaml

pyzmq

green	Enable gevent compatibility with zeromq

pyzor

gevent	Enable support for the gevent based handler
mysql	Enables mysql support
pyzord	enable support for pyzord
redis	Enables redis support

rarfile

compressed	Enables the module to support compressed v3 archives by calling the app-arch/unrar.

rdflib

redland	enable support for Redland triplestore

restkit

cli	Install the restcli command line interface/tool, based on dev-python/ipython

scrapy

boto	Add support for Amazon S3 via dev-python/boto
ibl	Use Instace Based Learning algorithm for automatic extraction

simplecv

shell	Enable the iPython SimpleCV shell

sphinx

net	enable internet capabilities

starcluster

epydoc	Enable build of apidocs in html using epydoc

sympy

imaging	Add support for dev-python/pillow
ipython	Add support for dev-python/ipython
mathml	Add support for mathml
pyglet	Use dev-python/pyglet for plots and print preview
symengine	Add support for a dev-python/symengine backend
texmacs	Add app-office/texmacs interface
theano	Add support for dev-python/theano

tdaemon

coverage	Enable code coverage support

translate-toolkit

html	Support conversion between po and html files
ical	Support conversion between po and ical files
ini	Support conversion between po and ini files
subtitles	Support conversion between po and sub files
yaml	Support YAML format

twisted

conch	include Twisted SSHv2 implementation
http2	include http2 support
serial	include serial port support

twisted-core

serial	include serial port support

vatnumber

vies	Enable VIES

ws4py

client	Install client modules
server	Install server modules

wxpython

doc	Install HTML wxWidgets docs and wxpython API reference.
examples	Install interactive demo module browser and sample applets.

zeep

async	Add async support
tornado	Add tornado support

zsi

twisted	add support for python-twisted (needs dev-python/twisted-core and dev-python/twisted-web)

dev-qt

assistant

exceptions	Add support for exceptions - like catching them inside the event loop (recommended by upstream)

designer

declarative	Build the qdeclarativeview plugin
exceptions	Add support for exceptions - like catching them inside the event loop (recommended by upstream)
phonon	Build the phononwidgets plugin
qt3support	Build the qt3supportwidgets plugin
webkit	Build the qwebview plugin

linguist

exceptions	Add support for exceptions - like catching them inside the event loop (recommended by upstream)

linguist-tools

qml	Enable QML support in lupdate

pixeltool

exceptions	Add support for exceptions - like catching them inside the event loop (recommended by upstream)

qdbusviewer

exceptions	Add support for exceptions - like catching them inside the event loop (recommended by upstream)

qdoc

qml	Enable QML/JS parsing support

qt-creator

android	Build plugin for Android devices
autotools	Enable autotools project manager plugin
baremetal	Build plugin for bare metal devices
bazaar	Add support for dev-vcs/bzr version control system
clangcodemodel	Build clang-based code model and refactoring plugins
clangstaticanalyzer	Build clang-based static analyzer plugin
clearcase	Add support for IBM ClearCase version control system (requires manual installation of ClearCase client)
cmake	Enable cmake project manager plugin
designer	Build widget designer plugin
glsl	Enable GLSL source code editor
ios	Build plugin for Apple iOS devices
mercurial	Add support for dev-vcs/mercurial version control system
modeling	Enable graphical model editor
nim	Enable Nim source code editor
perforce	Add support for Perforce version control system (requires manual installation of Perforce client)
python	Enable Python source code editor
qbs	Enable QBS project manager plugin
qnx	Build plugin for QNX devices
scxml	Enable graphical SCXML editor
systemd	Add support for retrieving application output from journald
valgrind	Add support for memory debugging using dev-util/valgrind
webengine	Use dev-qt/qtwebengine to view documentation
winrt	Build plugin for WinRT devices

qt-docs

charts	Install documentation for dev-qt/qtcharts
datavis	Install documentation for dev-qt/qtdatavis3d
networkauth	Install documentation for dev-qt/qtnetworkauth
script	Install documentation for dev-qt/qtscript
speech	Install documentation for dev-qt/qtspeech
virtualkeyboard	Install documentation for dev-qt/qtvirtualkeyboard
webengine	Install documentation for dev-qt/qtwebengine

qt-meta

qt3support	Enable the Qt3Support library for Qt4

qt3d

gles2	Use GLES 2.0 or later instead of full OpenGL
qml	Build QML/QtQuick bindings

qt3support

exceptions	Add support for exceptions - like catching them inside the event loop (recommended by upstream)

qtbearer

exceptions	Add support for exceptions - like catching them inside the event loop (recommended by upstream)

qtbluetooth

qml	Build QML/QtQuick bindings and imports

qtcharts

qml	Build QML/QtQuick bindings and imports

qtcore

exceptions	Add support for exceptions - like catching them inside the event loop (recommended by upstream)
glib	Enable dev-libs/glib eventloop support
qt3support	Enable the Qt3Support libraries for Qt4. Note that this does not mean you can compile pure Qt3 programs with Qt4.
systemd	Enable native journald logging support

qtdatavis3d

gles2	Use GLES 2.0 or later instead of full OpenGL
qml	Build QML/QtQuick bindings and imports

qtdbus

exceptions	Add support for exceptions - like catching them inside the event loop (recommended by upstream)

qtdeclarative

exceptions	Add support for exceptions - like catching them inside the event loop (recommended by upstream)
gles2	Use GLES 2.0 or later instead of full OpenGL
localstorage	Build the LocalStorage import for QtQuick (requires QtSql)
qt3support	Enable the Qt3Support libraries for Qt4. Note that this does not mean you can compile pure Qt3 programs with Qt4.
webkit	Build the WebView QML component
widgets	Enable QtWidgets support
xml	Build the XmlListModel import for QtQuick (requires QtXmlPatterns)

qtdemo

dbus	Build QtDBus examples and demos
declarative	Build QtDeclarative examples and demos
exceptions	Add support for exceptions - like catching them inside the event loop (recommended by upstream)
multimedia	Build QtMultimedia examples and demos
opengl	Build QtOpenGL examples and demos
phonon	Build Phonon examples and demos
webkit	Build QtWebKit examples and demos
xmlpatterns	Build QtXmlPatterns examples and demos

qtdiag

network	Report network information
widgets	Report widget style information

qtgui

egl	Enable EGL integration
eglfs	Build the EGL Full Screen/Single Surface platform plugin
evdev	Enable support for input devices via evdev
exceptions	Add support for exceptions - like catching them inside the event loop (recommended by upstream)
gles2	Use GLES 2.0 or later instead of full OpenGL
glib	Enable integration with the dev-libs/glib event loop
gtkstyle	Build a widgets style that mimics the active GTK+ theme
ibus	Build the IBus input method plugin
libinput	Enable support for input devices via dev-libs/libinput
qt3support	Enable the Qt3Support libraries for Qt4. Note that this does not mean you can compile pure Qt3 programs with Qt4.
trace	Build the 'trace' graphicssystem engine which allows to record all drawing operations into a trace buffer. The trace can be replayed later with the qttracereplay tool.
tslib	Enable support for touchscreen devices via x11-libs/tslib
tuio	Build plugin to receive touch events over the TUIO protocol
xcb	Build the XCB platform plugin and enable X11 integration

qthelp

compat	Build the extra compatibility layer required by a few packages, see http://blog.qt.io/blog/2010/06/22/qt-assistant-compat-version-available-as-extra-source-package/
exceptions	Add support for exceptions - like catching them inside the event loop (recommended by upstream)

qtmultimedia

exceptions	Add support for exceptions - like catching them inside the event loop (recommended by upstream)
gles2	Use GLES 2.0 or later instead of full OpenGL
gstreamer	Enable audio support via media-libs/gstreamer using SLOT 1.0
qml	Build QML/QtQuick bindings and imports
widgets	Build the QtMultimediaWidgets module

qtnetwork

bindist	Disable EC support via dev-libs/openssl
connman	Enable net-misc/connman-based bearer plugin
libproxy	Use net-libs/libproxy for automatic HTTP/SOCKS proxy configuration
networkmanager	Enable net-misc/networkmanager-based bearer plugin

qtopengl

egl	Use EGL instead of GLX to manage OpenGL contexts
exceptions	Add support for exceptions - like catching them inside the event loop (recommended by upstream)
gles2	Use GLES 2.0 or later instead of full OpenGL
qt3support	Enable the Qt3Support libraries for Qt4

qtpositioning

geoclue	Use enhanced location information from app-misc/geoclue
qml	Build QML bindings

qtprintsupport

gles2	Use GLES 2.0 or later instead of full OpenGL

qtquickcontrols

widgets	Enable QtWidgets support

qtquickcontrols2

widgets	Enable QtWidgets support

qtscript

exceptions	Add support for exceptions - like catching them inside the event loop (recommended by upstream)
scripttools	Build the QtScriptTools module (requires QtWidgets)

qtsensors

qml	Build QML bindings

qtsql

exceptions	Add support for exceptions - like catching them inside the event loop (recommended by upstream)
qt3support	Enable the Qt3Support libraries for Qt4

qtsvg

exceptions	Add support for exceptions - like catching them inside the event loop (recommended by upstream)

qttest

exceptions	Add support for exceptions - like catching them inside the event loop (recommended by upstream)

qtvirtualkeyboard

handwriting	Adds handwriting recognition integration support

qtwayland

libinput	Enable support for input devices via dev-libs/libinput

qtwebchannel

qml	Build QML/QtQuick bindings and imports

qtwebengine

geolocation	Enable physical position determination via dev-qt/qtpositioning
pax_kernel	Enable building under a PaX enabled kernel
system-ffmpeg	Use the system-wide media-video/ffmpeg instead of bundled.
system-icu	Use the system-wide dev-libs/icu instead of bundled.
widgets	Enable QtWidgets support

qtwebkit

exceptions	Add support for exceptions - like catching them inside the event loop (recommended by upstream)
geolocation	Enable physical position determination via dev-qt/qtpositioning
gles2	Use GLES 2.0 or later instead of full OpenGL
gstreamer	Enable HTML5 audio/video support via media-libs/gstreamer using SLOT 1.0
gstreamer010	Enable HTML5 audio/video support via media-libs/gstreamer using SLOT 0.10
multimedia	Enable HTML5 audio/video support via dev-qt/qtmultimedia
orientation	Enable device orientation detection via dev-qt/qtsensors
printsupport	Enable printing via dev-qt/qtprintsupport
qml	Build QML/QtQuick bindings
webchannel	Enable integration with dev-qt/qtwebchannel
webp	Add support for WebP image format

qtwebsockets

qml	Build QML bindings

qtwidgets

gles2	Use GLES 2.0 or later instead of full OpenGL

dev-ros

rosbag

lz4	Add support for lz4 compressed bags.

rosconsole

glog	Use dev-cpp/glog as log backend.
log4cxx	Use dev-libs/log4cxx as log backend.

dev-ruby

barby

cairo	Add support for writing images (PNG, PS, EPS and, if supported, PDF and SVG) using dev-ruby/rcairo. Not available on JRuby.
png	Add support for writing PNG images using dev-ruby/chunky_png.
prawn	Add support for writing PDF documents using dev-ruby/prawn.
qrcode	Add support for QRCode 2D codes using dev-ruby/rqrcode.
rmagick	Add support for writing images (among others PNG, GIF and JPEG) using dev-ruby/rmagick. Not available on JRuby.

facter

dmi	Use sys-apps/dmidecode to determine hardware system properties
pciutils	Use sys-apps/pciutils to determine hardware system properties
virt	Use app-emulation/virt-what for virtual machine detection

faraday_middleware

mashify	Include FaradayMiddleware::Mashify
oauth	Include FaradayMiddleware::OAuth
parsexml	Include FaradayMiddleware::ParseXml
rashify	Include FaradayMiddleware::Rashify

maruku

highlight	Enable source code highlighting via dev-ruby/syntax

net-ssh

sodium	Use dev-libs/libsodium via dev-ruby/rbnacl for Ed25519 support

rails

asset-pipeline	Also install the default components for the asset pipeline. These are not required but they are activated automatically in new Rails projects by default.

rrdtool-bindings

graph	Enable support for graphing functions

rspec-core

highlight	Enable source code highlighting via dev-ruby/coderay

ruby-sdl

image	Enable media-libs/sdl-image support
mixer	Enable media-libs/sdl-mixer support
sge	Enable sdl-sge support

rubygems

server	Install support for the rubygems server

dev-scheme

gauche-gl

cg	Enable NVidia Cg binding

gauche-gtk

glgd	Enable GL graph draw

guile

debug-freelist	Include garbage collector freelist debugging code
debug-malloc	Include malloc debugging code
deprecated	Enable deprecated features
discouraged	(implied by deprecated) enable merely discouraged features
networking	Include networking interfaces
regex	Include regular expression interfaces

kawa

awt	Assume AWT is available
echo2	Enable support for the Echo2 web toolkit with dev-java/echo2
frontend	Build "kawa" front-end program using sys-libs/readline
jemacs	Build JEmacs
krl	Build BRL emulation and KRL
sax	Assume SAX2 is available with dev-java/sax
servlets	Build support for generating servlets with dev-java/servletapi
swing	Assume Swing is available
swt	Assume SWT is available with dev-java/swt
xqtests	Support XQuery Test Suite

racket

backtrace	Support GC backtrace dumps
futures	Enable racket/future library for fine-grained hardware parallelism
places	Enable racket/place library for share-nothing parallelism and message-passing communication. Compared to futures, places are heavyweight, but they have a simpler performance model.
plot	Enable plot libraries
threads	Enable support for green threads

scm

arrays	Support for arrays, uniform-arrays and uniform-vectors.
bignums	Support for large precision integers.
cautious	SCM will always check the number of arguments to interpreted closures.
dynamic-linking	Be able to load compiled files while running.
engineering-notation	Floats to display in engineering notation (exponents always multiples of 3) instead of scientific notation.
gsubr	generalized c arguments: for arbitrary (more then 11) arguments to C functions.
inexact	Support for floating point numbers.
ioext	Commonly available I/O extensions: line I/O, file positioning, file delete and rename, and directory functions.
libscm	Build and install libscm.a and related headers
macro	C level support for hygienic and referentially transparent macros (syntax-rules macros).
regex	String regular expression matching.
unix	Support for: nice, acct, lstat, readlink, symlink, mknod and sync.

slib

gambit	Support for gambit scheme implementation
scm	Support for scm scheme implementation

dev-tcltk

expect-lite

debug	pull in packages needed for runtime interactive debugger

tktreectrl

shellicon	shellicon extension

dev-tex

abntex

lyx	Install with app-office/lyx layout

biblatex

biber	Install the unicode compatible backend processor

circuit_macros

script	Install cm2pdf to automatically create a correctly sized PDF from a circuit_macro m4 source

dot2texi

pgf	Enable support for dev-tex/pgf (The TeX Portable Graphic Format)
pstricks	Enable pstricks support

pythontex

highlighting	Syntax highlighting using dev-python/pygments

dev-texlive

texlive-basic

luajittex	Add support for LuaJitTeX: LuaTeX based on LuaJIT which is usually faster.

dev-util

android-ndk

legacy-toolchains	Install legacy toolchains
target-32	Support for 32-bit targets
target-64	Support for 64-bit targets

anjuta

devhelp	Enable devhelp integration
glade	Build glade plugin for anjuta
packagekit	Use packagekit to search for missing tools
terminal	Enable terminal plugin based on x11-libs/vte

apitrace

cli	Enable command line interface
egl	Enable EGL support
system-snappy	Link dynamic against app-arch/snappy

bazel

tools	Install extra bazel tools to build from sources

bitcoin-tx

knots	Build enhanced Bitcoin Knots version, rather than Bitcoin Core
ljr	Enable Luke Dashjr's patches

buildbot

irc	Add support for status delivery through an ircbot.
mail	Add support for watching a maildir for commits.
manhole	Add support for manhole (debug over ssh)

bustle

interactivetests	Build interactive test programs
threaded	Build with support for multithreaded execution.

catalyst

ccache	Enables ccache support

cccc

apidoc	Build software docs with doxygen/graphviz and metrics with cccc
mfc	Add patch for MFC dialect options

cmake

server	Enable cmake-server support.
system-jsoncpp	Use system copy of dev-libs/jsoncpp instead of bundled one.

coccigrep

vim	Install the coccigrep vim plugin

codeblocks

contrib	Build additional contrib components

cppcheck

htmlreport	install cppcheck-htmlreport

ctags

json	Enable JSON output support
xml	Enable XML parsing support
yaml	Enable YAML parsing support

cwdiff

a2ps	install app-text/a2ps for postscript output
mercurial	install hg wdiff alias for dev-vcs/mercurial

devhelp

gedit	Install plugin for app-editors/gedit

dialog

minimal	Disable library, install command-line program only

diffoscope

R	Use dev-lang/R
binutils	Use sys-devel/binutils
colord	Use x11-misc/colord
cpio	Use app-arch/cpio
diff	Use sys-apps/diffutils
docx	Use app-text/docx2txt
dtc	Use sys-apps/dtc
e2fsprogs	Use sys-fs/e2fsprogs
file	Use sys-apps/file
find	Use sys-apps/findutils
gettext	Use sys-devel/gettext
gpg	Use app-crypt/gnupg
haskell	Use dev-lang/ghc
hex	Use app-editors/vim-core
iso	Use virtual/cdrtools
llvm	Use sys-devel/llvm
opendocument	Use app-text/odt2txt
pascal	Use dev-lang/fpc
rpm	Use app-arch/rpm
squashfs	Use sys-fs/squashfs-tools
ssh	Use net-misc/openssh
tar	Use app-arch/tar
tcpdump	Use net-analyzer/tcpdump
xz	Use app-arch/xz-utils
zip	Use app-arch/unzip

edb-debugger

graphviz	Add support for the Graphviz library
legacy-mem-write	Probe if writes to /proc/PID/mem are broken.
pax_kernel	Enable building under a PaX enabled kernel

electron

lto	Build with link time optimization enabled
pic	Disable optimized assembly code that is not PIC friendly
proprietary-codecs	Enable proprietary codecs like H.264, MP3
system-ffmpeg	Use system ffmpeg instead of the bundled one
tcmalloc	Use bundled tcmalloc instead of system malloc

emilpro

system-binutils	Use the gentoo binutils instead of building against an unpatched vanilla version

fatrace

powertop	Add powetop integration

geany

gtk3	Use GTK+3 instead of GTK+2
vte	Enable Terminal support (x11-libs/vte)

geany-plugins

autoclose	Enable the autoclose plugin.
automark	Enable the automark plugin
commander	Enable the commander plugin which provides a command panel for rapid access to any action.
ctags	Enable ctags plugin
debugger	Enable the debugger plugin which interfaces with sys-devel/gdb
defineformat	Enable the defineformat plugin.
enchant	Enable spell checking using enchant
gpg	Enable geanypg plugin which integrates GPG using app-crypt/gpgme
gtk3	Use GTK+3 instead of GTK+2
gtkspell	Use gtkspell for dictionary support in GeanyVC
keyrecord	Enable the keyrecord plugin
multiterm	Enable the multiterm plugin
overview	Enable overview plugin
pretty-printer	Enable pretty-printer plugin
scope	Enable the scope plugin which is a graphical GDB front-end
soup	Enable updatechecker and geniuspaste plugins which require net-libs/libsoup

global

vim	Integrate the GNU GLOBAL source code tag system with Vim

google-perftools

debug	Build a set of libraries with debug support (so-called debugalloc). These are available by default but are not needed unless you're actually developing using tcmalloc.
largepages	Use (experimental) larger pages for tcmalloc, this increases memory usage, but should speed up the allocation/free operations.
minimal	Only build the tcmalloc_minimal library, ignoring the heap checker and the profilers.
optimisememory	To build libtcmalloc with smaller internal caches.

gtk-doc

highlight	Enable source code highlighting
vim	Enable source code highlighting through app-editors/vim

idea-community

custom-jdk	Install and use IntelliJ's custom JRE.

idea-ultimate

custom-jdk	Install and use IntelliJ's custom JRE.

intel-ocl-sdk

android	Install android related files
system-boost	Use system boost (dev-libs/boost) instead of bundled one
system-clang	Use system clang (sys-devel/clang) instead of bundled one
system-qt	Use system Qt (sys-devel-qtcore, sys-devel/qtgui) instead of bundled one
system-tbb	Use sytem Thread Building Blocks (dev-cpp/tbb) instead of bundled one
tools	Install Intel Offline Compiler

kdevelop

gdbui	Enable GUI for attaching GDB to a running process
okteta	Enable hex editor plugin via kde-apps/okteta
qmake	Enable support for QMake build system
reviewboard	Enable reviewboard support
webkit	Enable deprecated dev-qt/qtwebkit instead of dev-qt/qtwebengine for integrated documentation
welcomepage	Enable welcome page, requires dev-qt/qtdeclarative

kdevplatform

reviewboard	Enable reviewboard support
welcomepage	Enable welcome page, requires dev-qt/qtdeclarative

ltrace

unwind	Use sys-libs/libunwind for frame unwinding support

lttng-tools

ust	Support LTTng-UST (Userspace Tracing)

massif-visualizer

callgraph	Enable detailed snapshot analysis using media-gfx/kgraphviewer

mdds

valgrind	Add support for memory debugging using dev-util/valgrind

mingw64-runtime

idl	Install idl files.
libraries	Build extra libraries.
tools	Build extra tools.

molecule

plugins	Add plugins provided by dev-util/molecule-plugins

nemiver

memoryview	Enable the optional hexadecimal memory inspection with app-editors/ghex

nvidia-cuda-sdk

cuda	Build CUDA binaries
opencl	Build OpenCL binaries

nvidia-cuda-toolkit

debugger	Installs the CUDA debugger
eclipse	Install plugins for eclipse
profiler	Installs the NVIDIA CUDA visual profiler

perf

demangle	Enable C++ symbol name demangling, using libbfd from sys-devel/binutils. When this flag is enabled, the package will have to be rebuilt after every version bump of binutils.
doc	Build documentation and man pages. With this USE flag disabled, the --help parameter for perf and its sub-tools will not be available. This is optional because it depends on a few documentation handling tools that are not always welcome on user systems.
numa	Enable NUMA support
perl	Add support for Perl as a scripting language for perf tools.
unwind	Use sys-libs/libunwind for frame unwinding support.

pkgconf

pkg-config	Install as a replacement for dev-util/pkgconfig

pkgconfig

internal-glib	Use internal copy of dev-libs/glib

pkgconfig-openbsd

pkg-config	Install as a replacement for dev-util/pkgconfig

radare2

system-capstone	Use dev-libs/capstone instead of bundled copy.

scanmem

gui	Enable the GameConqueror GUI

schroot

btrfs	Enable support for chroots using btrfs snapshots.
dchroot	Enables the building of a wrapper named "dchroot", replacing sys-apps/dchroot.
lvm	Enable support for chroots using LVM snapshots.

squashdelta

lz4	Enable support for LZ4 compression using app-arch/lz4

squashmerge

lz4	Enable support for LZ4 compression using app-arch/lz4

strace

aio	Enable dev-libs/libaio support for tracing Asynchronous I/O operations
unwind	Enable stack backtraces (-k flag) via sys-libs/libunwind

suse-build

symlink	Provide compatibility symlinks with original openSUSE package (might clash with other packages)

sysdig

modules	Build kernel modules needed for tracing local events. Disable this only if you intend to use sysdig purely to work with dumpfiles.

sysprof

systemd	Build the sysprofd daemon service, required to run the UI without root permissions. Relies on sys-apps/systemd running as the init system.

systemtap

libvirt	Support probing of libvirt domains.

trace-cmd

udis86	Enable support for dev-libs/udis86 disassembler library

dev-vcs

bzr

sftp	Enable sftp support

bzr-gtk

gpg	Support signing with GnuPG.
nautilus	Integrate with Nautilus file manager

cssc

valgrind	Enable usage of dev-util/valgrind in tests

cvs

server	Enable server support

cvs2svn

bazaar	Support for dev-vcs/bzr

cvsync

gcrypt	Use dev-libs/libgcrypt for hash functions.
mhash	Use app-crypt/mhash for hash functions.
openssl	Use dev-libs/openssl for hash functions.

darcs

diff	Use 'lcs' for diff building.
http	Use the pure Haskell HTTP package for HTTP support.
network-uri	Get Network.URI from the network-uri package.
terminfo	Use the terminfo package for enhanced console support.
threaded	Use threading and SMP support.

fossil

fusefs	Enable the Fuse Filesystem
json	Enable the JSON API of Fossil's wiki
legacy-mv-rm	Enable legacy behavior for mv/rm (skip checkout files).
miniz	Use the bundled miniz for compression instead of zlib. Incompatible with ssl.
system-sqlite	Use the system SQLite instead of the bundled one
tcl-private-stubs	Enable Tcl integration via private stubs mechanism
tcl-stubs	Enable Tcl integration via stubs library mechanism
th1-docs	Enable TH1 for embedded documentation pages
th1-hooks	Enable TH1 hooks for commands and web pages

git

blksha1	Use the new optimized SHA1 implementation
cgi	Install gitweb too
curl	Support fetching and pushing (requires webdav too) over http:// and https:// protocols
gpg	Pull in gnupg for signing -- without gnupg, attempts at signing will fail at runtime!
highlight	GitWeb support for app-text/highlight
mediawiki	Support pulling and pushing from MediaWiki
mediawiki-experimental	Add experimental patches for improved MediaWiki support
pcre-jit	Enable JIT for pcre
ppcsha1	Make use of a bundled routine that is optimized for the PPC arch
subversion	Include git-svn for dev-vcs/subversion support
tk	Include the 'gitk' and 'git gui' tools
webdav	Adds support for push'ing to HTTP/HTTPS repositories via DAV

git-annex

assistant	Enable git-annex assistant and watch command
benchmark	Enable benchmarking
concurrentoutput	Use concurrent-output library (experimental)
magicmime	Use libmagic to determine file MIME types
network-uri	Get Network.URI from the network-uri package.
pairing	Enable pairing of git annex repositories
s3	Enable Amazon S3 remote
torrentparser	Use haskell torrent library to parse torrent files
webapp	Enable git-annex webapp
webdav	Enable webdav remote

gitg

glade	Install a glade catalog file
python	Install Python bindings for those plugins requiring it.

gitolite

contrib	Install user-contributed files
tools	Install tools to e.g. convert a Gitosis config to gitolite or one to check if your setup is gitolite >= 3.x compatible

gitolite-gentoo

contrib	Install user-contributed files
tools	Install tools to e.g. convert a Gitosis config to gitolite or one to check if your setup is gitolite >= 3.x compatible

kdesvn

man	Build and install man pages

mercurial

bugzilla	Support bugzilla integration.
gpg	Support signing with GnuPG.
tk	Install dev-lang/tk for hgk script.

qct

bazaar	Support for dev-vcs/bzr
mercurial	Support for dev-vcs/mercurial
monotone	Support for dev-vcs/monotone

rabbitvcs

caja	Enable extension for mate-base/caja
cli	Eanble console based frontend
diff	Use for diff command dev-util/meld
gedit	Enable plugin for app-editors/gedit
nautilus	Enable extension for gnome-base/nautilus
thunar	Enable extension for xfce-base/thunar

subversion

ctypes-python	Build and install Ctypes Python bindings
dso	Enable runtime module search
extras	Install extra scripts (examples, tools, hooks)
http	Enable http support using net-libs/serf
kwallet	Enable encrypted storage of passwords with kde-frameworks/kwallet

games-action

beathazardultra

bundled-libs	Use the upstream provided bundled libraries.

chromium-bsu

mixer	Enables media-libs/sdl-mixer sound backend instead of media-libs/openal one.

d1x-rebirth

demo	Use the demo data instead of the full game
l10n_de	Provides German translations for the game's briefings, robot descriptions, and outro of the original campaign
music	Support for ingame music
opl3-musicpack	Include alternate version of the game's music, recorded with the Yamaha YMF262 OPL3 soundchip
sc55-musicpack	Include alternate version of the game's music, recorded with the Roland Sound Canvas SC-55 MIDI module

d2x-rebirth

demo	Install games-action/descent2-demodata as well
l10n_de	Provides German translations for the game's briefings, robot descriptions, and outro of the original campaign
music	Support for ingame music
opl3-musicpack	Include alternate version of the game's music, recorded with the Yamaha YMF262 OPL3 soundchip
sc55-musicpack	Include alternate version of the game's music, recorded with the Roland Sound Canvas SC-55 MIDI module

dxx-rebirth

data	Install data files
descent1	Install Descent 1 resources and executable
descent2	Install Descent 2 resources and executable
l10n_de	Provides German translations for the game's briefings, robot descriptions, and outro of the original campaign
music	Enable music support
opl3-musicpack	Include alternate version of the game's music, recorded with the Yamaha YMF262 OPL3 soundchip
sc55-musicpack	Include alternate version of the game's music, recorded with the Roland Sound Canvas SC-55 MIDI module
textures	Include high resolution (640x480) backgrounds, briefing images and fonts (Descent 1)

hotline-miami

bundled-libs	Use bundled libraries.
launcher	Install qt launcher

minetest

leveldb	Enable LevelDB backend
luajit	Use dev-lang/luajit instead of dev-lang/lua
postgres	Optionally use PostgreSQL as map backend
redis	Enable redis backend via dev-libs/hiredis
server	Build minetest server
spatial	Enable SpatialIndex AreaStore backend

solar2

bundled-libs	Use the upstream provided bundled libraries.

super-hexagon

bundled-libs	Use the upstream provided bundled libraries.

supermariowar

server	Compile and install Super Mario War server files

supertuxkart

fribidi	Support for right-to-left languages
recorder	Enable recording with media-libs/libopenglrecorder
wiimote	Support for wiimote input devices

swordandsworcery

bundled-libs	Use the upstream provided bundled libraries.

trine2

bundled-libs	Use bundled libraries.
launcher	Install gtk+ launcher

games-arcade

bomns

editor	enables building the level editor

burgerspace

network	Enable client-server support

commandergenius

tremor	Use media-libs/tremor as ogg decoder instead of media-libs/libvorbis

jumpnbump

music	Enable playing of background music

lbreakout2

themes	Install additional themes

moleinvasion

music	Download and install the music files

performous

midi	Enable MIDI I/O support
songs	Install a few demo songs
tools	Install tools
webcam	Enable Webcam support

savagewheels

fmod	Enable the fmod music and sound effects library

slimevolley

net	Enable network support

tuxanci

physfs	Use dev-games/physfs instead of dev-libs/libzip to load compressed data
sound	Enable sound

games-board

cockatrice

client	Build with client
oracle	Build with oracle
server	Compile server support

crafty

no-opts	Don't try to enable crazy CFLAG options

freedoko

backgrounds	Install additional background images
gnomecards	Install the gnome-games card set
kdecards	Install the KDE card set
net	Enable network game support
openclipartcards	Install the openclipartcards card set
pysolcards	Install the PySol card set
xskatcards	Install the XSkat card set

grhino

gtp	Install the GTP (Go/Game Text Protocol) frontend

knights

speech	Enable text-to-speech support

pasang-emas

extras	Install some extra themes

pioneers

help	Enable gnome ingame help via scrollkeeper

pysolfc

extra-cardsets	Install extra cardsets
sound	Enable sound support using dev-python/pygame

spider

athena	Enable athena widgets

stockfish

armv7	Build for armv7; enables PIE
general-32	Generic unoptimized 32-bits build
general-64	Generic unoptimized 64-bits build
optimize	Enable upstream -O3 optimizations (default enabled)

tablebase-syzygy

6-pieces	Install tablebases for 6 pieces (huge!)

xboard

default-font	Install the default font that xboard uses
zippy	Enable experimental zippy client

games-emulation

dolphin

egl	Enable EGL support
evdev	Enable evdev input support
llvm	Enable the LLVM-based disassembler for debugger mode
log	Increase logging output
lto	Add support for link-time optimizations.

dosbox

glide	Enable unofficial Glide emulation via media-libs/openglide

fceux

logo	Enable the ability to add a logo screen when creating AVIs

generator

sdlaudio	Enable SDL Audio

higan

icarus	Build icarus library manager
udev	Enable udev based input

m64py

7z	Ensure support for .7z archives.
rar	Ensure support for .rar archives.

mednafen

debugger	Build with internal debugger
pax_kernel	Triggers a paxmarking of the binary

mupen64plus

audio-sdl	Enable SDL audio plugin.
input-sdl	Enable SDL input plugin.
rsp-hle	Enable HLE RSP plugin.
ui-console	Enable default console UI.
ui-m64py	Enable PyQt5 UI using games-emulation/m64py.
video-glide64mk2	Enable Glide64mk2 video plugin.
video-rice	Enable Rice video plugin.

mupen64plus-core

debugger	Build the debugger
gles2	Use GLES2 instead of OpenGL
new-dynarec	Enable new experimental dynamic recompiler implementation (only for x86 and arm)
osd	Overlay emulator messages using on-screen-display

mupen64plus-video-glide64mk2

gles2	Use GLES2 instead of OpenGL
hires	Support hi-resolution textures (requires dev-libs/boost)

mupen64plus-video-rice

gles2	Use GLES2 instead of OpenGL

nestopia

gui	Enable GUI

pcsxr

cdio	Use libcdio for CD support
sdl	Use SDL sound backend (other parts of SDL are used unconditionally)

ppsspp

headless	Build headless version of the PPSSPP
system-ffmpeg	Use the system-wide media-video/ffmpeg instead of bundled

sdlmame

arcade	Enable the Multiple Arcade Machine Emulator for arcade games support
mess	Enable the Multi Emulator Super System for game system support
tools	Build development tools shared between sdlmame and sdlmess

snes9x

netplay	Enable playing ROMs over the network (not recommended)
xrandr	Enable support for the X xrandr extension

vbam

link	Enable GBA linking functionality

yabause

pic	disable optimized assembly code that is not PIC friendly

zsnes

debug	Enable the builtin debugger
pax_kernel	Triggers a paxmarking of the binary

games-engines

frobtads

tads2compiler	Build TADS2 compiler
tads3compiler	Build TADS3 compiler

odamex

master	Build master server target (advertises odamex server list)
odalaunch	Build the wxwidgets based launcher.
portmidi	Enable portmidi support.
server	Build server target.

openmw

devtools	Install development tools like bsatool, esmtool and opencs.

renpy

development	Install IDE for game developers and an empty game template

scummvm

fluidsynth	compile with support for fluidsynth
mpeg2	enable mpeg2 codec for cutscenes
unsupported	enable unsupported and/or broken game engines (you're on your own)

solarus

doc	Install doxygen developer documentation.
luajit	Use LuaJIT instead of default Lua.

stratagus

fluidsynth	compile with support for fluidsynth

games-fps

alienarena

vidmode	Link against x11-libs/libXxf86vm. Required for full-screen support.

darkplaces

cdsound	Enables using CD audio in the engine
demo	Uses the demo data from quake1 (quake1-demodata)
lights	Install and setup the updated light maps
textures	Install and setup the updated textures

doom-data

doomsday	Add wrapper to run it within doomsday

doom3

dedicated	install only as a dedicated game server
roe	Adds support for the Resurrection of Evil expansion

doomsday

demo	Install launcher dor doom1.wad from games-fps/doom-data
doom	Install launcher for jdoom game
fluidsynth	Build the FluidSynth sound driver
freedoom	Install launcher for doom1.wad from games-fps/freedoom
heretic	Install launcher for jheretic game
hexen	Install launcher for jhexen game
resources	Enable support for games-fps/doomsday-resources in jdoom launcher
snowberry	Install Snowberry doomsday front-end
tools	Build additional tools such as doomsday-shell, md2tool and texc

duke3d

demo	Install the demo files
pic	disable optimized assembly code that is not PIC friendly

duke3d-data

gog	Extract the data from the GOG.com installer.

eduke32

demo	Install games-fps/duke3d-demodata as well
gtk	Compile with gtk launcher
offensive	Include optional XXX texture pack (needs USE 'textures')
opl-musicpack	Include optional OPL (AdLib) music pack
samples	Install samples
sc55-musicpack	Include optional Roland SC-55 music pack
server	Compile with server support
textures	Include optional high-resolution textures (needs USE 'opengl')
tools	Build several tools for modding and development
vpx	Enable support for WebM VP8 Codecs (needs USE 'opengl')

lsdldoom

freedoom	Install games-fps/freedoom wad file
net	Enables network game support
shareware	Install games-fps/doom-data for shareware wad file

nexuiz

maps	Install the community map pack

quake2-icculus

demo	Install the demo files (quake2-demodata) and configure for use
qmax	Build the pretty version (quake max)
rogue	Build support for the 'Ground Zero' Mission Pack (rogue)
xatrix	Build support for the 'The Reckoning' Mission Pack (xatrix)

quake3

mumble	Adds player-location (positional audio) support to VoIP
teamarena	Adds support for Team Arena expansion pack
voice	Adds VoIP support

quake3-bin

teamarena	Adds support for Team Arena expansion pack

quake3-demo

dedicated	install only as a dedicated game serer

quakeforge

wildmidi	enable libWildMidi support
xdg	enable XDG support

qudos

demo	Install the demo files (quake2-demodata) and configure for use
mods	Build support for the quake2 mission packs
qmax	Build the pretty version (quake max)
textures	Install the enhanced textures (quake2-textures)

rott

demo	Install the shareware version

sauerbraten

server	Compile server support

turtlearena

mumble	Adds player-location (positional audio) support to VoIP
server	Build server target
voice	Adds VoIP support

unreal-tournament-goty

S3TC	Add the extra fancy textures to UT ... only works on certain cards (nvidia/ati/s3)

urbanterror

altgamma	Alternative way for gamma setting with modesetting driver
client	Build binary for client (includes code for non-dedicated server)
mumble	Use Mumble for ingame VoIP (experimental)
opus	Use opus as sound codec
server	Build binary for dedicated server
skeetshootmod	Build support for skeetshoot mod for specific maps
voip	Use ioq3 ingame VoIP (experimental)

worldofpadman

maps	Install extra maps (PadPack)

xonotic

ode	Enable support for physics engine from dev-games/ode

games-kids

crayon-physics

bundled-libs	Use the upstream provided bundled libraries.

games-misc

katawa-shoujo

system-renpy	Use games-engines/renpy instead of the bundled one (experimental)

little-inferno

bundled-libs	Use bundled libraries.

ponysay

fish-completion	Enable fish completion support
non-free	Install non-free ponies (i.e. from the MLP franchise)

xcowsay

fortune	Installs the fortune-mod xcow binary

games-mud

tf

atcp	enable ATCP support.
gmcp	enable GMCP support.
option102	enable telnet option 102 support.

games-puzzle

cuyo

music	Enable playing of background music

nightsky

bundled-libs	Use the upstream provided bundled libraries.

numptyphysics

user-levels	Install some fun user-created levels

pingus

music	Enable playing of background music

sgt-puzzles

gtk3	Use x11-libs/gtk+:3 instead of x11-libs/gtk+:2

tiny-and-big

bundled-libs	Use the upstream provided bundled libraries.

xlogical

alt_gfx	Use alternate graphics which are closer to the original Amiga version

games-roguelike

FTL

bundled-libs	Use bundled libraries.

angband

sound	Enable and install sounds

nethack

experimental	Enable experimental features (showscore and status_hilite)

stone-soup

luajit	Use dev-lang/luajit as scripting backend instead of dev-lang/lua.
ncurses	Enable for console (uses ncurses) based build. (can be enabled on top of tiles)
tiles	Enable for graphical (tiled) build. (can be enabled on top of ncurses)

tomenet

server	Compile server support

games-rpg

arx-fatalis-data

gog	Extract the data from the GOG.com installer.

arx-libertatis

c++0x	Build ROOT using the C++11 standard.
crash-reporter	Build a dev-qt/qtgui-based tool that allows to submit crash information to the upstream backtracker.
debug	Enable asserts and debug logging.
static	Link libraries statically, currently only media-libs/glew
tools	Build tools that can extract the game's data and save files.
unity-build	Build everything in one big source file, allowing for faster build times and better optimizations at the cost of higher memory usage.

daimonin-client

music	Install extra music

drascula

sound	Install optional audio files

dreamweb

doc	High-resolution scans of the written material in the original UK game box

dungeon-defenders

bundled-libs	Use the upstream provided bundled libraries.

eternal-lands-data

bloodsuckermaps	Will install Bloodsucker's Maps in place of the official map files
music	Enables in-game music
sound	Enables in-game sound effects

grimrock

bundled-libs	Use bundled libraries.

kqlives

cheats	Enable cheating mode

manaplus

mumble	Enable support for voice chat
pugixml	Use dev-libs/pugixml for XML parsing isntead of dev-libs/libxml2
sdl2	Use libsdl2 instead of libsdl

sumwars

tools	Builds editor tools

to-the-moon

bundled-libs	Use bundled libraries

games-simulation

flightgear

dbus	Enable screensaver DBus interaction
gdal	Enable alternative terrain engine based on pagedLOD using sci-libs/gdal
qt5	Build Qt5 launcher application
udev	Enable event-based Input devices through virtual/udev
utils	Build various utilities (fgpanel, fgviewer among others)

openrct2

multiplayer	Enable multiplayer functionality
twitch	Enable Twitch support

openttd

aplaymidi	Enables midi music in game, using aplaymidi as an external player
dedicated	Build only the openttd server, and not the client.
lzo	Enables LZO compression for savegames. This is only needed to load extremely old savegames. (versions before 0.2)
openmedia	Enables the free open media sets: OpenGFX, OpenSFX, OpenMSX, removing the requirement for proprietary TTD assets to play OpenTTD.

singularity

music	Install music files

games-sports

speed-dreams

xrandr	Enable support for the X xrandr extension

xmoto

editor	Depend on inkscape, scripts to convert svg to level (svg2lvl)

games-strategy

0ad

editor	Include Atlas scenario editor projects
lobby	Enable the use of net-libs/gloox and the multiplayer lobby
nvtt	Support for some uncompressed data formats via media-gfx/nvidia-texture-tools (might be needed for some mods)

defcon-demo

system-libs	Use system libraries instead of the ones included in the upstream distribution.

freeciv

aimodules	Support for dynamically loadable AI modules (server-side)
auth	Add authentication capability via mysql, postgres or sqlite3
mapimg	Additional mag image toolkit via media-gfx/imagemagick
modpack	Build the freeciv-modpack-program to download/install mods
server	Enable server support. Disabling this will also make it impossible to start local games.
sound	Add support for sound provided by media-libs/sdl-mixer
system-lua	Use dev-lang/lua instead of the bundled liblua

freesynd

devtools	Build development tools

heroes3

maps	Installs optional map data
music	Installs optional music data
sounds	Installs optional sound data

ja2-stracciatella

editor	Adds necessary file to run the editor
linguas_ru_gold	Support for russian gold ja2 version

liquidwar6

doc	Convert the info pages to html
gles2	Enable OpenGL ES 2.0 support
gtk	Used to display error/critical messages
maps	Install extra maps
ogg	Enable mod-ogg via media-libs/sdl-mixer (currently the only sound provider)
readline	Enable interactive script shell for hacking

megaglest

editor	Build map editor
fribidi	Enable FriBIDi support
model-viewer	Build model viewer
streflop	Use the library streflop. Out of synchs may occur if not enabled.
tools	Build model import/export tools
unicode	Use unicode strings for wxwidgets
wxuniversal	Use the wxUniversal port which implements the various GUI controls by drawing them itself

naev

mixer	Enables media-libs/sdl-mixer sound backend in addition to media-libs/openal one.

seven-kingdoms

network	Enable support for multiplayer via media-libs/sdl-net

ufo-ai

editor	Build map editor

uqm

music	download and install music files (large)
remix	download and install music remix files (large)
voice	download and install voice files (large)

wesnoth

fribidi	Support for right-to-left languages
server	Enable compilation of server

games-util

gslist

web	Enable the web interface

pyfa

graph	Enable support for graphs

wit

fuse	Enable image mount support via fuse

gnome-base

gconf

ldap	Build backend which enables default mail accounts, addressbooks and calendars for Evolution to be configured using each user's LDAP entry."

gdm

fprint	Enables experimental fingerprint authentication using sys-auth/fprintd
plymouth	Enable support for smooth transition from sys-boot/plymouth

gnome

classic	Install gnome-extra/gnome-shell-extensions for the Gnome Shell Classic mode
extras	Install additional GNOME applications

gnome-common

autoconf-archive	Pull in sys-devel/autoconf-archive for ax_*.m4 files instead of installing them from the gnome-common tarball

gnome-control-center

colord	Support color management using x11-misc/colord
gnome-online-accounts	Enable configuration panel for net-libs/gnome-online-accounts accounts
ibus	Enable support for enhanced input methods through app-i18n/ibus

gnome-desktop

license-docs	Install help files documenting GNOME's licenses

gnome-extra-apps

games	Install Gnome Games
share	Install the gnome-extra/gnome-user-share personal file sharing tool
shotwell	Install the media-gfx/shotwell photo manager
tracker	Install the app-misc/tracker indexer and the GNOME packages that require it

gnome-keyring

ssh-agent	Use GNOME Keyring to unlock SSH keys. Recommended unless you are using ECDSA or Ed25519 keys.

gnome-light

gnome-shell	Install gnome-base/gnome-shell and x11-wm/mutter for the standard GNOME 3 desktop mode

gnome-settings-daemon

colord	Support color management using x11-misc/colord
openrc-force	Skip systemd dependency (#480336), enabling this flag will become your setup to be fully unsupported by upstream and downstream Gnome team. Do not try to enable it unless completely needed

gnome-shell

browser-extension	Ensure the presence of extensions.gnome.org native connector gnome-extra/chrome-gnome-shell
ibus	Enable support for enhanced input methods through app-i18n/ibus
openrc-force	Skip systemd dependency (#480336), enabling this flag will become your setup to be fully unsupported by upstream and downstream Gnome team. Do not try to enable it unless completely needed

gvfs

afp	Enables support for accessing AFP (Apple Filing Protocol) network shares
archive	Enables support for accessing files in archives transparently via app-arch/libarchive
bluray	Enable playback of Blu-ray filesystems using media-libs/libbluray
fuse	Enables fuse mount points in $HOME/.gvfs for legacy application access
gnome-online-accounts	Enable configuration panel for net-libs/gnome-online-accounts accounts
google	Enables support for accessing Google accounts via dev-libs/libgdata
http	Enable the HTTP/DAV backend using net-libs/libsoup
nfs	Enable NFS client support via net-fs/libnfs.
udev	Enable udev base replacement code for cdda feature

libglade

tools	Install libglade-convert Python script.

libgnomecanvas

glade	Enable glade support

librsvg

tools	Build svg viewer tool

nautilus

packagekit	Use packagekit to search for programs to open unknown file types
previewer	Use gnome-extra/sushi to preview files from the file mananger
sendto	Enable the nautilus-sendto extension to send files to various locations/devices
tracker	Add support for app-misc/tracker search

orbit

pic	Force libname-server-2 to be built as PIC; needed on hardened systems

gnome-extra

cinnamon-control-center

colord	Support color management using x11-misc/colord

cinnamon-settings-daemon

colord	Support color management using x11-misc/colord

evolution-data-server

api-doc-extras	Build documentation for private APIs
berkdb	sys-libs/db support needed to migrate old (pre-3.12 evolution versions) addressbook data
gnome-online-accounts	Enable net-libs/gnome-online-accounts based Google authentication support
google	Enable internal Google authentication support. If gnome-online-accounts is enabled and used, this is not necessary, but both can be supported at the same time with different setup at runtime
weather	Enable optional weather calendar support

gnome-builder

clang	Provide integration with sys-devel/clang for best possible C/C++ autocompletion, semantic highlighting, symbol resolving, and diagnostics support
git	Provide support for the Git version control system via dev-libs/libgit2-glib (such as setup of Git for New Project, direct cloning for Open Project and changed lines indicators in the editor gutter)
sysprof	Provide an integrated profiler via dev-util/sysprof
vala	Provide an autoindenter, autocompletion, diagnostics, and symbol resolver for Vala
webkit	Enable net-libs/webkit-gtk using plugins support and the HTML/Markdown previewer plugin

gnome-color-manager

packagekit	Enable support for the distro-neutral package manager GUI app-admin/packagekit

gnome-commander

chm	Enable metadata support for Microsoft Compiled HTML Help files
gsf	Add metadata support for OLE, OLE2 and ODF
pdf	Add metadata support for PDF
python	Add support for python plugins
samba	Add support for SAMBA (Windows File and Printer sharing)
taglib	Add metadata support for ID3, Vorbis, FLAC and APE
unique	Enable single instance support using dev-libs/libunique

gnome-dvb-daemon

totem	Build a plugin for media-video/totem

gnome-system-monitor

systemd	Display sys-apps/systemd metadata, e.g. unit names, for running processes

libgda

canvas	Enable support for x11-libs/goocanvas
http	Enable embedded net-libs/libsoup based server
json	Enable support for JSON format
mdb	Enable support for Microsoft Access database using app-office/mdbtools
reports	Install tools for generating graphical reports
sourceview	Enable support for x11-libs/gtksourceview

libgsf

gtk	Enable use of gdk in thumbnailer

nemo

packagekit	Use packagekit to search for programs to open unknown file types
tracker	Add support for app-misc/tracker search

nm-applet

gcr	Enable advanced certificate chooser, requires app-crypt/gcr
modemmanager	Enable support for mobile broadband devices using net-misc/modemmanager
teamd	Enable teamd configuration editor

sushi

office	Support viewing file formats such as generated by app-office/libreoffice

synapse

plugins	Build support for plugins using librest
zeitgeist	Add support for Zeitgeist event tracking system

zeitgeist

datahub	Use build datahub for passive event injection
downloads-monitor	Monitor the XDG_DOWNLOAD_DIRECTORY
fts	Enable the full text search extension
sql-debug	Enable SQL debugging
telepathy	Enable telepathy framework as data source

gnustep-apps

gemas

projectcenter	Build and install plugin for gnustep-apps/projectcenter

gworkspace

gwmetadata	Enable the metadata indexing and searching system

gnustep-base

gnustep-back-art

xim	Enable X11 XiM input method

gnustep-back-cairo

xim	Enable X11 XiM input method

gnustep-back-xlib

xim	Enable X11 XiM input method

gnustep-gui

speech	Audio support using app-accessibility/flite

gnustep-make

libobjc2	Enables use of the GNUstep Objective-C runtime (gnustep-base/libobjc2) with non-fragile ABI and sys-devel/clang compiler
native-exceptions	Enables use of the native Objective-C exception support (@try/@catch/@finally) built-in objective-c exceptions with compilers that support it

libobjc2

boehm-gc	Enable Hans Boehm's garbage collector (dev-libs/boehm-gc). Not recommended by upstream

kde-apps

akonadi

designer	Install plugin for dev-qt/designer
tools	Install tools for developers and testing

analitza

eigen	Enable dev-cpp/eigen mathematical templates support

ark

zip	Enable ZIP archive support via dev-libs/libzip

artikulate

qtmedia	Enable playback via Qt5Multimedia

cantor

R	Enable dev-lang/R backend support
analitza	Enable kde-apps/analitza backend support
julia	Enable dev-lang/julia backend support
qalculate	Enable sci-libs/libqalculate backend support

dolphin

thumbnail	Enables video thumbnail generation

dolphin-plugins

bazaar	Enable support for the bazaar VCS
dropbox	Enable support for the dropbox fileviewer plugin
git	Enable support for the git VCS
mercurial	Enable support for the mercurial VCS

gwenview

fits	Enable support for NASA's sci-libs/cfitsio library
kipi	Support for the KDE Image Plugin Interface

k3b

emovix	Enable burning support for eMoviX images

kalzium

editor	Enable the embedded molecule editor/viewer
solver	Enable the equation solver

kanagram

speech	Enable text-to-speech support

kate

addons	Build and install additional plugins

kde-apps-meta

pim	Pull in KDE PIM suite
sdk	Pull in developer-specific meta-packages

kdeadmin-meta

cron	Installs KDE application for virtual/cron configuration

kdebase-kioslaves

sftp	Enable SFTP protocol support using net-libs/libssh

kdegraphics-mobipocket

thumbnail	Enables thumbnail generation

kdemultimedia-meta

cdrom	Include packages for optical discs

kdenlive

freesound	Enable freesound.org credentials support via dev-qt/qtwebkit to download files
gles2	Use GLES 2.0 or later instead of full OpenGL
jogshuttle	Enable support for Jog-Shuttle devices

kdepim-addons

importwizard	Enable additional import plugins for kde-apps/akonadi-import-wizard

kdepim-runtime

speech	Enable text-to-speech support

kdeutils-meta

floppy	Install kde-apps/kfloppy to format and create DOS or ext2fs filesystems in a floppy.

keditbookmarks

man	Build and install man pages

kget

bittorrent	Enable bittorrent transfer plugin through net-libs/libktorrent
gpg	Enable signature verification by GpgME++ via app-crypt/gpgme
mms	Enable MMS (Microsoft Media Server) plugin through media-libs/libmms

kig

geogebra	Support files created by sci-mathematics/geogebra
scripting	Support Python scripting

kio-extras

activities	Enable activities kioslave and fileitem plugin
htmlthumbs	Enable HTML thumbnail previews via dev-qt/qtwebengine
man	Enable manpages kioslave
phonon	Enable file audio preview plugin using media-libs/phonon
sftp	Enable SFTP protocol support using net-libs/libssh

kmag

keyboardfocus	Enable keyboard focus tracking

konqueror

activities	Enable kactivities support
speech	Build text-to-speech plugin

kopete

addbookmarks	Automatically add incoming urls to bookmarks.
autoreplace	Automatically replace selected text
contactnotes	Enables writing personal notes for contacts.
gadu	Enable the Gadu protocol handler.
groupwise	Enable the Groupwise protocol handler.
highlight	Allows you to specify highlights on specific events.
history	Enables saving chat history.
latex	Embed latex formatted text into messages.
meanwhile	Enable the Sametime protocol handler.
nowlistening	Shows song you currently listen to in your status/etc. Bindings for many players.
otr	Allows crypting your chat (drugs and talking nonsense are considered as good alternatives ;]).
pipes	Send messages to external pipe.
privacy	Filter for incoming messages
statistics	Everybody loves statistic graphs, especially cake ones. ;]
testbed	Enable the testbed protocol.
texteffect	Various fancy text effects for your messages (don't ever consider writing us with this enabled ;]).
translator	Translate incoming and outgoing messages.
urlpicpreview	Enables in conversation pictures preview.
webpresence	Show your status and some more information on web.
winpopup	Enable pop-up messages sending on windows. (same as good old "net send" messages ;])
yahoo	Enable yahoo protocol support.
zeroconf	Enable Link-Local Messaging via the bonjour protocol.

kpimtextedit

designer	Build plugins for dev-qt/designer
speech	Enable text-to-speech support

kstars

fits	Enable support for NASA's sci-libs/cfitsio library
indi	Enable support for Astronomical control library using libindi
wcs	Enable support for World Coordinate System library using wcslib
xplanet	Enable support for Xplanet

ktp-accounts-kcm

experimental	Enables disabled telepathy services (currently only steam)

ktp-common-internals

otr	Enable support for encrypted conversations using Off-The-Records messaging
sso	Enable support for Single sign-on through KAccounts

ktp-text-ui

speech	Enable incoming messages to be read out using text-to-speech

kwave

opus	Enable Opus audio codec support
qtmedia	Enable playback via Qt5Multimedia

libkdepim

designer	Build plugins for dev-qt/designer

mailcommon

designer	Build plugins for dev-qt/designer

marble

aprs	Enable support for APRS data sources
designer	Install plugin for dev-qt/designer
phonon	Enable sound support via media-libs/phonon
shapefile	Enable support for ESRI shapefiles

okteta

designer	Build plugins for dev-qt/designer

okular

chm	Enable support for Microsoft Compiled HTML Help files
epub	Enable E-Book support via app-text/ebook-tools
image-backend	Enable image viewing support
markdown	Enable Markdown support via app-text/discount
mobi	Enable mobipocket support
mobile	Enable Plasma mobile support
plucker	Enable Plucker E-Book for Palm OS devices support
share	Enable support for a share menu using dev-libs/purpose
speech	Enable text-to-speech support

pimcommon

designer	Build plugins for dev-qt/designer

spectacle

kipi	Enable support for the KDE Image Plugin Interface
share	Enable support for a share menu using dev-libs/purpose

step

qalculate	Enable the libqalculate library for unit conversion

kde-frameworks

frameworkintegration

appstream	Enable AppStream software metadata support

kconfigwidgets

man	Build and install man pages

kded

man	Build and install man pages

kdelibs

qt3support	Enable kde3support/qt3support for very old applications

kdesignerplugin

designer	Build KF5 widgets plugin for QtDesigner
webkit	Build kdewebkit plugin for QtDesigner

kfilemetadata

epub	Enable support for reading EPUB ebook metadata
office	Enable support for reading ODF and OOXML metadata

kimageformats

eps	Support the EPS graphics file format

kinit

caps	Capabilities support for improved security and better OOM handling
man	Build and install man pages

kio

kwallet	Enable permanent storage of passwords for kpasswdserver with kde-frameworks/kwallet

knotifications

speech	Enable text-to-speech notification support

knotifyconfig

phonon	Add sound support via media-libs/phonon

kpackage

man	Build and install man pages

kservice

man	Build and install man pages

ktexteditor

editorconfig	Enable support for EditorConfig configuration files

ktextwidgets

speech	Enable text-to-speech support

kwallet

gpg	Support wallets with GnuPG encryption in addition to the default blowfish-encrypted file
man	Build and install man pages

kxmlgui

attica	Enable support for kde-frameworks/attica

networkmanager-qt

teamd	Enable Teamd control support

plasma

gles2	Use GLES 2.0 or later instead of full OpenGL

sonnet

aspell	Enable the app-text/aspell spell-checking backend
hunspell	Enable the app-text/hunspell spell-checking backend

kde-misc

kdeconnect

app	Enable experimental kcapp frontend
wayland	Enable kwin_wayland support for mousepad plugin using kde-frameworks/kwayland

kimtoy

scim	Enable Smart Common Input Method support

kio-gdrive

kaccounts	Use kde-apps/kaccounts-integration backend (default) instead of dev-libs/qtkeychain

kmarkdownwebview

webkit	Use dev-qt/qtwebkit instead of dev-qt/qtwebengine

tellico

discid	Add support for reading disc IDs from audio CDs

kde-plasma

kde-cli-tools

kdesu	Build graphical frontend for kde-frameworks/kdesu

kde-gtk-config

gtk3	Add support for gtk+3-based applications.

kdeplasma-addons

share	Enable applet for quickly sharing data to a variety of sources

kinfocenter

gles2	Show OpenGL ES information in kinfocenter
pci	Show advanced PCI information

kmenuedit

hotkeys	Enable support for hotkey editing

kwin

gles2	Use OpenGL ES 2 instead of full GL
multimedia	Enable effect video button in desktop effects KCM

libksysguard

detailedmemory	Enable display of detailed memory information using dev-qt/qtwebkit.

plasma-desktop

appstream	Enable AppStream software metadata support
gtk2	Add support for gtk+2-based applications using legacy xembed systray icons via libappindicator.
gtk3	Add support for gtk+3-based applications using legacy xembed systray icons via libappindicator.
ibus	Use ibus input method via app-i18n/ibus
legacy-systray	Add support for applications using legacy xembed systray icons.
mouse	Enable mouse KCM
scim	Enable applets that use app-i18n/scim
touchpad	Enable touchpad KCM

plasma-meta

crypt	Pull in kde-plasma/plasma-vault for encrypted vaults integration
display-manager	Pull in a graphical display manager
grub	Pull in Breeze theme for sys-boot/grub
gtk	Enable Breeze widget style and KCM for GTK2 and GTK3
pam	Enable support for kwallet auto-unlocking
plymouth	Pull in Breeze theme for sys-boot/plymouth
pulseaudio	Install Plasma applet for PulseAudio volume management
sddm	Pull in the x11-misc/sddm display manager and KCM
sdk	Pull in kde-plasma/plasma-sdk for Plasma development
wallpapers	Install wallpapers for the Plasma Workspace

plasma-nm

modemmanager	Enable support for mobile broadband devices
openconnect	Build support for the OpenConnect VPN client
teamd	Enable Teamd control support

plasma-workspace

appstream	Enable AppStream software metadata support
geolocation	Enables dataengine providing location information
prison	Enable support for barcodes/QRcodes
qalculate	Enable Qalculate runner using sci-libs/libqalculate

powerdevil

consolekit	Enable sys-auth/consolekit support instead of logind session tracking
wireless	Enable wireless energy saving actions via kde-frameworks/bluez-qt and kde-frameworks/networkmanager-qt

systemsettings

classic	Enable classic mode plugin, requires kde-frameworks/khtml

lxde-base

lxdm

consolekit	Enables support for authorization using consolekit
gtk3	Use GTK+3 instead of 2

lxterminal

gtk3	Use GTK+3 instead of GTK+2

lxqt-base

lxqt-meta

about	Install lxqt-base/lxqt-about
admin	Install lxqt-base/lxqt-admin
filemanager	Install x11-misc/pcmanfm-qt file manager
icons	Install an icon theme
lightdm	Install x11-misc/lightdm display manager
lximage	Install media-gfx/lximage-qt image viewer
minimal	Do not install x11-wm/openbox window manager
oxygen	Prefer kde-frameworks/oxygen-icons (default)
powermanagement	Install lxqt-base/lxqt-powermanagement package
sddm	Install x11-misc/sddm display manager
ssh-askpass	Install lxqt-base/lxqt-openssh-askpass user password prompt tool
sudo	Install lxqt-base/lxqt-sudo

lxqt-panel

clock	Build clock plugin
colorpicker	Build colorpicker plugin
cpuload	Build cpuload plugin
desktopswitch	Build desktopswitch plugin
dom	Build dom plugin
kbindicator	Build kbindicator plugin
mainmenu	Build mainmenu plugin
mount	Build mount plugin
networkmonitor	Build networkmonitor plugin
quicklaunch	Build quicklaunch plugin
sensors	Build sensors plugin
showdesktop	Build showdesktop plugin
statusnotifier	Build statusnotifier plugin
sysstat	Build sysstat plugin
taskbar	Build taskbar plugin
tray	Build tray plugin
volume	Build volume plugin
worldclock	Build worldclock plugin

mail-client

alot

doc	Install user manual and API documentation

alpine

chappa	enhance alpine by applying Eduardo Chappa's patches
onlyalpine	installs only the alpine binary, so it does not collied with pico and/or pine
passfile	Adds support for caching passwords into a file between sessions
smime	Enable support for S/MIME

balsa

crypt	Adds support for GnuPG encryption
gtkhtml	Use gtkhtml for HTML rendering
gtkspell	Use gtkspell for dictionary support
rubrica	Adds support for rubrica addressbook

claws-mail

archive	Enable archiving plugin
bogofilter	Build mail-filter/bogofilter plugin
gdata	Enable plugin for access to Google data providers
gtk3	Build support for GTK+3
libcanberra	Enable sound notification in connection with USE=notification
libindicate	Enable notification through DBUS in connection with USE=notification
libnotify	Enable notification on the desktop in connection with USE=notification
notification	Notification for new mail in different way, see also USE flags libcanberra, libindicate and libnotify
pgp	Enable PGP support
sieve	Build plugin for sieve filter support
smime	Build plugin for S/MIME support
spam-report	Enable plugin for spam reporting to various services
spamassassin	Build mail-filter/spamassassin plugin
valgrind	Add support for memory debugging using valgrind

evolution

archive	Enable archives support in attachments via app-arch/gnome-autoar
bogofilter	Build mail-filter/bogofilter plugin
crypt	Enable GPG encryption support using app-crypt/gnupg and app-crypt/pinentry
geolocation	Enable support for displaying contacts on a map inside evolution using media-libs/libchamplain
highlight	Enable text highlighting plugin
ldap	Enable support for fetching contacts from an LDAP or Active Directory server using net-nds/openldap
spamassassin	Build mail-filter/spamassassin plugin
weather	Enable optional weather calendar support

mail-notification

sylpheed	Enable support for MH mailboxes used by mail-client/sylpheed

mutt

berkdb	Enable sys-libs/db database backend for header caching
crypt	Add support for encryption -- using mcrypt or gpg where applicable
gdbm	Enable sys-libs/gdbm database backend for header caching
gpg	Enable support for app-crypt/gpgme
gpgme	Build gpgme backend to support S/MIME, PGP/MIME and traditional/inline PGP
hcache	Enable header cache, one database backend needs to be enabled
lmdb	Enable dev-db/lmdb database backend for header caching
notmuch	Enable support for net-mail/notmuch
pgp_classic	Build classic_pgp backend to support PGP/MIME and traditional/inline PGP
pop	Enable support for POP3 mailboxes
sidebar	Enable the sidebar feature
smime	Enable support for smime
smime_classic	Build classic_smime backend to support S/MIME
smtp	Enable support for direct SMTP delivery
tokyocabinet	Enable dev-db/tokyocabinet database backend for header caching

nail

kerberos	If network is enabled, this adds support for GSSAPI login on IMAP through virtual/krb5.
net	Enable support for network protocols (POP, IMAP and SMTP). If you only need to send mail with the local Transport Agent, disabling this will get you support for only /usr/sbin/sendmail call.
ssl	If network is enabled, this adds support for S/MIME and SSL/TLS-powered protocols through dev-libs/openssl.

neomutt

berkdb	Enable BDB (Berkley DB) backend for header caching
crypt	Add support for encryption -- using mcrypt or gpg where applicable
gdbm	Enable GDBM (GNU dbm) backend for header caching
gpg	Enable support for app-crypt/gpgme
gpgme	Build gpgme backend to support S/MIME, PGP/MIME and traditional/inline PGP
kyotocabinet	Enable Kyoto Cabinet database backend for header caching
lmdb	Enable LMDB (Lightning Memory-Mapped Database) backend for header caching
notmuch	Enable support for net-mail/notmuch
pgp_classic	Build classic_pgp backend to support PGP/MIME and traditional/inline PGP
qdbm	Enable QDBM (Quicker Database Manager) database backend for header caching
smime	Enable support for smime
smime_classic	Build classic_smime backend to support S/MIME
tokyocabinet	Enable Tokyo Cabinet database backend for header caching

roundcube

enigma	Add dependencies to support server-side GnuPG signing and/or encryption through the enigma plugin
ldap	Add dependencies to support connecting to an LDAP address book server
managesieve	Add dependencies to support the sieverules plugin

sylpheed

oniguruma	Use dev-libs/oniguruma for regular expression

thunderbird

bindist	Disable official Thunderbird branding (icons, name) which are not binary-redistributable according to upstream.
crypt	Enable encryption support with enigmail
custom-optimization	Build with user-specified compiler optimizations (-Os, -O0, -O1, -O2, -O3) from CFLAGS (unsupported)
gtk2	Use the cairo-gtk2 rendering engine instead of the default cairo-gtk3
jemalloc	Enable or disable jemalloc
jemalloc3	Enable or disable jemalloc3 (forced-on when supported prior to 38.0)
lightning	Enable app-global calendar support (note 38.0 and above bundles calendar support when this flag is off)
minimal	Remove the software development kit and headers
mozdom	Enable Mozilla's DOM inspector
rust	Enable support for using rust compiler (experimental)
system-cairo	Use the system-wide x11-libs/cairo instead of bundled.
system-harfbuzz	Use the system-wide media-libs/harfbuzz and media-gfx/graphite2 instead of bundled.
system-icu	Use the system-wide dev-libs/icu instead of bundled.
system-jpeg	Use the system-wide media-libs/libjpeg-turbo instead of bundled.
system-libevent	Use the system-wide dev-libs/libevent instead of bundled.
system-libvpx	Use the system-wide media-libs/libvpx instead of bundled.
system-sqlite	Use the system-wide dev-db/sqlite installation with secure-delete enabled

thunderbird-bin

crashreporter	Enable crash reporter for bugs

trojita

password	Store passwords securely via dev-libs/qtkeychain

mail-filter

MailScanner

exim	Set mail-mta/exim to used MTA
postfix	Set mail-mta/postfix to used MTA
spamassassin	Enable usage of mail-filter/spamassassin for spam protection

amavisd-new

courier	Add courier support
dkim	Add DomainKeys Identified Mail support
qmail	Add qmail support
razor	Add support for mail-filter/razor
spamassassin	Add support for mail-filter/spamassassin
zmq	Add support for zeromq sockets

ask

procmail	Adds support for mail-filter/procmail

assp

spf	Adds support for Sender Policy Framework
srs	Adds support for Sender Rewriting Scheme

bogofilter

tokyocabinet	Enable Tokyo Cabinet database support

clamassassin

clamd	Use the app-antivirus/clamav daemon for virus checking
subject-rewrite	Adds support for subject rewriting

dcc

rrdtool	Enable net-analyzer/rrdtool interface scripts

dspam

daemon	Enable support for DSPAM to run in --daemon mode
debug	Enable debugging support (don't enable this unless something needs testing!)
domain-scale	Build for domain scale setups - puts data to $HOME/data/domain.com/user
hash	Enable support for the file-orientated hash driver
large-scale	Build for large scale setups - puts data to $HOME/data/u/s/user
small-scale	Build for small scale setups - puts data to $HOME/data/user
user-homedirs	Build with user homedir support
virtual-users	Build with virtual-users support

libmilter

poll	Use poll instead of select

maildrop

authlib	Add courier-authlib support
dovecot	Add dovecot authentication support
tools	Install maildirmake and deliverquota tools
trashquota	Count deleted messages as part of the maildir quota

mimedefang

poll	Use poll instead of select

opendkim

ldap	Enable openldap as a dataset facilitator or keys, determining domains to sign for, and any other dataset that opendkim supports.
lmdb	Add support for using dev-db/lmdb
lua	Enables control over signature verification, filtering and policy to be controlled by user defined lua scripts.
memcached	Add support for using dev-libs/libmemcached
opendbx	Use opendbx backend to facilitate dataset driven OpenDKIM configuration options like stats, bodylengthdb, etc. against a wide variety of database types
poll	Use poll() instead of select() for the provided asynchronous resolver library.
sasl	Used to authenticate to a LDAP server in various ways if required.
unbound	Use the unbound dnssec library to perform DKIM DNS queries.

opendmarc

reports	Install the reports binaries: expire, import, reports, params
spf	Use the mail-filter/libspf2 for Sender Policy Framework checking

opensmtpd-extras

filter-clamav	filter for scanning with app-antivirus/clamav
filter-dkim-signer	filter for adding DKIM signatures to outgoing messages
filter-dnsbl	filter for checking hosts against the DNS black lists
filter-lua	filter for interfacing with dev-lang/lua
filter-monkey	filter for arbitrarily rejecting random emails
filter-pause	filter to pause on new connections
filter-perl	filter for interfacing with dev-lang/perl
filter-python	filter for interfacing with dev-lang/python
filter-regex	filter for regular expression matching
filter-spamassassin	filter for scanning with mail-filter/spamassassin
filter-stub	stub filter
filter-trace	trace filter
filter-void	void filter
luajit	Use JIT for Lua via dev-lang/luajit instead of dev-lang/lua
queue-null	null queue
queue-python	queue for interfacing with dev-lang/python
queue-ram	ram queue
queue-stub	stub queue
scheduler-python	schedulre for interfacing with python
scheduler-ram	ram scheduler
scheduler-stub	stub scheduler
table-ldap	table for lookups with net-nds/openldap
table-mysql	table for lookups with virtual/mysql
table-passwd	table for lookups using /etc/passwd
table-postgres	table for lookups with dev-db/postgresql
table-python	table for interfacing with dev-lang/python
table-redis	table for lookups with dev-db/redis
table-socketmap	table for lookups using a socket map
table-sqlite	table for lookups with dev-db/sqlite3
table-stub	stub table

postfwd

tools	Install additional tools for testing postfwd

postgrey

targrey	Enables the targrey patch

qmail-scanner

spamassassin	Build faster mail-filter/spamassassin checks into qmail-scanner

rmilter

dkim	Enable support for DomainKeys Identified Mail
memcached	Enable support for memcached

rspamd

fann	Enable neural network plugin (requires sci-mathematics/fann).
jemalloc	Use dev-libs/jemalloc for allocations
pcre2	Use dev-libs/libpcre2

spamassassin

bayes	Require a database (MySQL, SQLite, Postgres, or BerkDB) backend to enable the Bayesian filtering database. If you use the Redis backend, you do not need to enable this flag (Redis support is enabled automatically, and has no external dependencies).
cron	Install a cron job to update SpamAssassin's rules daily.
qmail	Build qmail functionality and docs

spamdyke

ssl	Enables TLS protocol for spamdyke

zdkimfilter

debug	Log process and signal information. Also leave the child process running for gdb examination.
opendbx	An alternate statistics based storage engine.

mail-mta

courier

fax	Enables fax support in the courier mail server
norewrite	Prevents courier mail server from mangling virtual user addresses when sending
web	Enable the web interface
webmail	Enable the webmail interface

exim

dane	Adds support for DNS-based Authentication of Named Entities
dcc	Adds support for Distributed Checksum Clearinghouse (DCC)
dkim	Adds support for DomainKeys Identified Mail (DKIM)
dlfunc	Install local_scan.h header to compile separate dlfunc libraries
dmarc	Adds support for DMARC
dnsdb	Adds support for a DNS search for a record whose domain name is the supplied query
dovecot-sasl	Adds support for Dovecot's authentication
dsn	Adds support for Delivery Status Notifications (DSN)
exiscan-acl	Patch providing support for content scanning
lmtp	Adds support for lmtp
mbx	Adds support for UW's mbx format
pkcs11	Require pkcs11 support in net-libs/gnutls with USE=gnutls
prdr	Adds support for Per-Recipient Data Response
proxy	Add support for being behind a proxy, such as HAProxy
redis	Adds support for querying dev-db/redis
spf	Adds support for Sender Policy Framework
srs	Adds support for Sender Rewriting Scheme
tpda	Adds support for Transport Post-Delivery Actions

msmtp

libsecret	Enable libsecret support to store login credentials
mta	Enable this to install as system-wide MTA

netqmail

authcram	Enable AUTHCRAM support
gencertdaily	Generate SSL certificates daily instead of hourly
highvolume	Prepare netqmail for high volume servers

opensmtpd

mta	Enable this to install as system-wide MTA

postfix

dovecot-sasl	Enable net-mail/dovecot protocol version 1 (server only) SASL implementation
eai	Add support for SMTPUTF8
ldap-bind	Add support for binding to LDAP backend using dev-libs/cyrus-sasl
lmdb	Add support for using dev-db/lmdb for lookup tables
memcached	Add support for using net-misc/memcached for lookup tables
vda	Add support for virtual delivery agent quota enforcing

qmail-ldap

cluster	Enable this if you want to have cluster support in qmail-ldap
gencertdaily	Generate SSL certificates daily instead of hourly
highvolume	Prepare qmail for high volume servers
rfc2307	Add support for RFC2307 compliant uid/gid attributes
rfc822	Add support for RFC822 compliant mail attributes

qpsmtpd

postfix	create user with permissions for proper postfix interaction

ssmtp

mta	Install symlinks for sendmail-compatible MTA.

mate-base

caja

gtk3	Build with GTK+3 instead of GTK+2
mate	Install x11-themes/mate-icon-theme which is needed when this package is used in the MATE desktop environment.
packagekit	Enable support for installing via app-admin/packagekit based on mimetype

libmatekbd

gtk3	Build with GTK+3 instead of GTK+2

mate

base	Install base MATE Desktop applications that are recommended for the most common usage; for example, this installs the file manager. Disable this and other USE flags if you want a more minimal MATE Desktop.
extras	Install additional MATE Desktop applications that are recommended for extended usage of the MATE Desktop as upstream sees it; for example, this installs MATE Desktop's office related applications. Disable this if you plan to use your own non-MATE Desktop alternatives or a custom mixture of MATE and non-MATE packages.
gtk3	Build all of MATE DE with GTK+3 instead of GTK+2
help	Install gnome-extra/yelp to handle in application help menus and documentation browsing
notification	Force notification daemon to default to MATE's notification daemon. Enabled by default. Disable if it causes conflicts with other installed desktop environments.
themes	Install MATE Desktop's themes; if you use other themes, you can disable this to spare some space and time.

mate-applets

gtk3	Build with GTK+3 instead of GTK+2

mate-applets-meta

appindicator	Pull in mate-extra/mate-indicator-applet for AppIndicator applet
gtk3	Make sure applets are built with GTK+3 instead of GTK+2
netspeed	Pull in net-analyzer/mate-netspeed for net speed monitoring applet
sensors	Pull in mate-extra/mate-sensors-applet for hw sensors applet

mate-control-center

appindicator	Add support for AppIndicator
gtk3	Build with GTK+3 instead of GTK+2

mate-desktop

gtk3	Build with GTK+3 instead of GTK+2

mate-panel

gtk3	Build with GTK+3 instead of GTK+2

mate-session-manager

gtk3	Build with GTK+3 instead of GTK+2
xtrans	Build with Xtrans support; WARNING: Disabling this flag will result in ICE binding on all interfaces

mate-settings-daemon

gtk3	Build with GTK+3 instead of GTK+2

mate-extra

caja-extensions

cdr	Add an extension to burn files to cds using app-cdr/brasero.
gajim	Add an extension to support net-im/gajim.
gksu	Add an extension to support opening files as root with x11-libs/gksu.
gtk3	Build with GTK+3 instead of GTK+2
image-converter	Add image conversion support.
mail	Add an extension to support e-mail functionality.
open-terminal	Add an extension to support an open terminal.
pidgin	Add an extension to support net-im/pidgin
share	Add an extension to support sharing files.
wallpaper	Add an extension to support setting an image as the current wallpaper

mate-indicator-applet

gtk3	Build with GTK+3 instead of GTK+2

mate-media

gtk3	Build with GTK+3 instead of GTK+2

mate-netbook

gtk3	Build with GTK+3 instead of GTK+2

mate-polkit

accountsservice	Support extraction of data from AccountsService
appindicator	Add support for AppIndicator
gtk3	Build with GTK+3 instead of GTK+2

mate-power-manager

applet	Enable building of the MATE applet.
gtk3	Build with GTK+3 instead of GTK+2
man	Build power manager's man page.
pm-utils	Adds support for suspend/resume using sys-power/upower-pm-utils instead of sys-power/upower

mate-screensaver

consolekit	Enable support for sys-auth/consolekit
gtk3	Build with GTK+3 instead of GTK+2

mate-sensors-applet

gtk3	Build with GTK+3 instead of GTK+2

mate-system-monitor

gtk3	Build with GTK+3 instead of GTK+2

mate-user-share

gtk3	Build with GTK+3 instead of GTK+2

mate-utils

applet	Enable the mate dictionary applet
gtk3	Build with GTK+3 instead of GTK+2

media-fonts

corefonts

tahoma	Also install the Tahoma font. Due to the lack of a free bold variant, this may render badly. See bug 184790.

culmus

ancient	Install ancient semitic scripts
fancy	Install fancy fonts
fontforge	Use media-gfx/fontforge to build fonts from source
taamey	Install taamey fonts

dejavu

fontforge	Use media-gfx/fontforge to build fonts from source

fontawesome

otf	Install the OpenType version of the font
ttf	Install the TrueType version of the font

infinality-ultimate-meta

free	Install fonts for the "free" preset
latin	Install additional latin fonts
minimal	Install a minimal set of fonts
ms	Install (free) fonts for the "ms" preset

intlfonts

bdf	Installs BDF fonts in addition to PCF

liberation-fonts

fontforge	Use media-gfx/fontforge to build fonts from source

montecarlo

bdf	Install BDF fonts in addition to PCF

mplus-outline-fonts

ipafont	Generates new fonts merged with media-fonts/ja-ipafonts

sil-charis

compact	Use more compactly spaced font

sil-gentium

compact	Also install more compact version of the font.

terminus-font

a-like-o	Changes view of letter 'a' - a looks like o (see homepage)
center-tilde	Place the '~' character vertically centered on the line instead of to the top.
distinct-l	ll2 variant with more distinctive l (lowercase L)
pcf	Install Portable Compiled Font (PCF) (required for X11)
pcf-unicode-only	Remove non-unicode PCF fonts that could be problematic. See bug #520222.
psf	Install PC Screen Font (PSF) with unicode data (for linux console)
quote	Changes view of quotes: symmetric ` and ' instead of asymmetric one (see homepage)
raw-font-data	Install RAW font data which should be compatible with most UNIX systems (you don't need this on linux)
ru-dv	Changes view of Russian letters 'de' and 've' (see homepage)
ru-g	Changes view of Russian letter 'ge' (see homepage)
ru-i	Changes view of Russian letter 'i' - not like Latin u, but like "mirrored" N (see homepage)
ru-k	Changes view of Russian letter 'k' (see homepage)

unifont

fontforge	Use media-gfx/fontforge to build fonts from source
utils	Install unifont utilities

media-gfx

album

plugins	Install optional plugins
themes	Install optional themes

alembic

boost	Use dev-libs/boost library
hdf5	Add support sci-libs/hdf5
pyalembic	Build pyalembic python bindings (needs dev-python/pyilmbase)
test	Build and run the test-suite
zlib	Use sys-libs/zlib for compressions

apngasm

7z	Enable support for 7zip compression
zopfli	Enable support for Zopfli compression

asymptote

boehm-gc	Enables using the Boehm-Demers-Weiser conservative garbage collector
offscreen	Enables off-screen rendering
sigsegv	Enables using dev-libs/libsigsegv

blender

boost	Enable features depending on boost.
bullet	Enable Bullet (Physics Engine).
collada	Add support for Collada interchange format through media-libs/opencollada.
colorio	Enable OpenColorIO color management through media-libs/opencolorio.
cuda	Build cycles renderer with nVidia CUDA support.
cycles	Build cycles renderer (requires media-libs/openimageio and dev-libs/boost).
dds	Adds DDS textures support to Blender.
doc	Build C and Python API documentation directly from the source code.
elbeem	Adds surface fluid simulation to Blender using El'Beem library.
game-engine	Adds Game Engine support to Blender.
headless	Build without graphical support (renderfarm, server mode only).
jemalloc	Use dev-libs/jemalloc for memory allocation.
llvm	Enable features depending on llvm.
man	Build and install man pages.
ndof	Enable NDOF input devices (SpaceNavigator and friends).
opencl	Allow OpenCL Graphics Acceleration. This may require extra graphics card drivers.
openimageio	Enable OpenImageIO Support
opennl	Enable use of Open Numerical Library
opensubdiv	Add rendering support form OpenSubdiv from Dreamworks Animation through media-libs/opensubdiv.
openvdb	Add GPU preview rendering. Only works with nVidia cards.
osl	Add support for OpenShadingLanguage scripting.
player	Build the Blender Player. THis requires the Game engine.
redcode	This flag add support for RED CODE camera digital format (5K HD images *.r3d) - EXPERIMENTAL.
test	Build the provided unit tests.
valgrind	Add support for memory debugging using dev-util/valgrind

comix

rar	Pulls app-arch/unrar for rar file support

cura

usb	Access 3D printers via USB

darktable

colord	Support color management using x11-misc/colord
flickr	Add support for uploading photos to flickr
geo	Enable geotagging support
kwallet	Enable encrypted storage of passwords with kde-frameworks/kwallet
libsecret	Enable libsecret support to store login credentials
opencl	Enable opencl support
pax_kernel	Triggers paxmarking of main darktable binary
webp	Enable WebP export support

digikam

addressbook	Enable akonadi contact integration
kipi	Enable support for media-plugins/kipi-plugins
lensfun	Enable support for media-libs/lensfun
marble	Enable support for geolocation using kde-apps/marble
mediaplayer	Enable support for media player using media-libs/qtav
panorama	Build the panorama plugin which requires media-gfx/hugin
semantic-desktop	Enable kde-frameworks/kfilemetadata support

enblend

gpu	GPU support for Enblend
image-cache	allow for processing of large images

eog-plugins

flickr	Enable uploading to Flickr
map	Enable world map display using media-libs/libchamplain
picasa	Enable uploading to Google's Picasa Web Albums

eom

gtk3	Build with GTK+3 instead of GTK+2

exact-image

swig	Adds Swig support dev-lang/swig

exiv2

webready	Support reading metadata over the internet

fbida

X	Install the Motif based image viewer "ida"
fbcon	Install the framebuffer image viewer "fbi"
ghostscript	Install the framebuffer ghostscript viewer "fbgs"
webp	Enable support for the WebP image format

fim

dia	Enable DIA file support via app-office/dia
imagemagick	Use convert from media-gfx/imagemagick as fallback file opener
xfig	Enable FIG file support via media-gfx/xfig

fontforge

truetype-debugger	Enable truetype debugger in fontforge

fotowall

webcam	Enable webcam support

freewrl

glew	Enable glew extensions
java	Build and install java EAI/SAI support library
libeai	Build EAI C library
opencl	Enable OpenCL support
osc	Allows for OSC-based control and communication between multiple freewrl instances
rbp	Enable support for Rigid Body Physics

geeqie

ffmpegthumbnailer	Enable video thumbnail support with media-video/ffmpegthumbnailer
gpu-accel	Enable GPU acceleration support - experimental
gtk3	Link against x11-libs/gtk+:3 instead of x11-libs/gtk+:2
map	Enable items map display - experimental

gimp

smp	Enable support for multiprocessors
vector-icons	Enable support for vector icons (experimental)

gmic

cli	Build CLI interface
opencv	Enable support for webcams using the OpenCV library

gnome-photos

flickr	Ensure runtime Flickr support

graphicsmagick

fpx	Enable FlashPix support with media-libs/libfpx
modules	Compile graphicsmagick with dynamically loadable modules
q16	Set storage quantum size to 16 (~2*memory)
q32	Set storage quantum size to 32 (~5*memory)
webp	Enable support for webp image format

graphviz

X	Builds lefty front-end, builds plugin -Txlib, and enables support for x11 in various other modules (needs cairo)
devil	Enables DevIL output plugin -Tdevil
gdk-pixbuf	Enables gdk-pixbuf2 plugin
gtk	Enables gtk+ output plugin -Tgtk (needs cairo)
gts	Enables support for gts
lasi	Enables PostScript output via media-libs/lasi, for plugin -Tlasi (needs cairo)
qt4	Builds gvedit front-end

gthumb

http	Enable webservice integration through net-libs/libsoup
json	Compile code that uses the libjson-glib library
slideshow	Enable slideshow plugin
webp	Enable support for webp image format

hugin

sift	automatically align images with media-gfx/autopano-sift-C

imagemagick

corefonts	Use media-fonts/corefonts which is required by some commands
fpx	Enable media-libs/libfpx support
hdri	enable High Dynamic Range Images formats
lqr	Enable experimental liquid rescale support using media-libs/liblqr
opencl	Enable OpenCL support
pango	Enable Pango support using x11-libs/pango
q32	Set quantum depth value to 32
q8	Set quantum depth value to 8
webp	Enable webp image format support using media-libs/libwebp

imageworsener

webp	enable webp image format support

inkscape

cdr	Enable support for CorelDRAW Diagrams
dia	pull in app-office/dia for dia import extension
inkjar	Enable support for OpenOffice.org SVG jar files
latex	pull in dependencies for LaTeX formulas
visio	Enable support for Microsoft Visio Diagrams
wpg	Enable support for WordPerfect Graphics

iscan-plugin-gt-f500

minimal	Install the firmware only, and not the plugin.

jpeg2ps

metric	Default to A4 paper size

k3d

3ds	Enable support for 3D Studio models
cuda	Use nvidia cuda toolkit for speeding up computations
gts	Add Support for the GNU Triangulated Surface Library sci-libs/gts

kphotoalbum

kipi	Support for the KDE Image Plugin Interface
map	Enable map display support using kde-apps/libkgeomap

krita

color-management	Enable color management via media-libs/opencolorio
qtmedia	Enable sound support for animations via dev-qt/qtmultimedia
vc	Enable support for dev-libs/vc, could be a significant speed boost

librecad

3d	Require all 2D coordinates stored as 3D
tools	Build additional tool programs: tff2lff

luminance-hdr

fits	Enable support for the FITS format

nip2

goffice	use x11-libs/goffice to show plots

nomacs

opencv	Build support for media-libs/opencv
zip	Build support for zip archives

nvidia-texture-tools

cg	Enable NVIDIA C graphics compiler toolkit plug-in
cuda	Enable NVIDIA CUDA toolkit support
glew	Enable support for The OpenGL Extension Wrangler Library (media-libs/glew)

openclipart

gzip	Compresses clip art using gzip

openexr_viewers

cg	Add support for nvidia's cg shaders

openvdb

abi3-compat	Enables compatibility with the old 3.x ABI. enabled by dfault.
openvdb-compression	Adds enhanced compression to files through dev-libs/c-blosc. Very useful so enabled by dfault.

photoqt

exiv2	Use media-gfx/exiv2 as optional dependency

pngcrush

system-libs	Use libpng and libz provided by system

potrace

metric	default to a4 paper size and metric measurement

povray

io-restrictions	POV-Ray's mechanism for control of I/O operations
mkl	Enable support for Intel Vector Math Library, part of sci-libs/mkl

pqiv

archive	Enable support for images in archives and cbX comic book files

pstoedit

emf	Enable media-libs/libemf support
flash	Enable media-libs/ming SWF support
pptx	Enable support for generating PowerPoint pptx files

qiv

magic	Use libmagic to determine mimetypes

qiviewer

webp	Build support for WEBP image format

sigal

s3	Enables support for the Amazon S3 service.

simple-scan

colord	Support color management using x11-misc/colord

slic3r

gui	Enable GUI

splashutils

fbcondecor	Support for the fbcondecor kernel patch.

ufraw

contrast	enable contrast setting option
fits	Enable support for the FITS image format through sci-libs/cfitsio
timezone	enable DST correction for file timestamps

xpaint

pgf	Support for loading PGF images

xsane

ocr	Enable support for Optical Character Recognition reader

yafaray

blender	install media-gfx/blender scripts

media-libs

a52dec

djbfft	Prefer D.J. Bernstein's library for fourier transforms

allegro

dumb	Enable media-libs/dumb module library support
physfs	Enable physfs support
vga	Enables the VGA graphics driver

alsa-lib

alisp	Enable support for ALISP (ALSA LISP) interpreter for advanced features.

alure

dumb	Enable media-libs/dumb module library support
fluidsynth	Enables Fluidsynth MIDI software synthesis

assimp

boost	Build assimp with boost support
samples	Build viewer library
tools	Build assimp tool binary

aubio

double-precision	Compile in double precision mode.

avidemux-core

nvenc	Adds support for NVIDIA Encoder (NVENC) API for hardware accelerated encoding on NVIDIA cards.
system-ffmpeg	Use the ffmpeg provided by the system.

avidemux-plugins

aften	Enable A/52 (AC-3) audio encoder support.
amr	Enable Adaptive Multi-Rate format support via media-libs/opencore-amr.
dcaenc	Enable DTS Coherent Acoustics audio encoder support via media-sound/dcaenc.
fdk	Adds support for encoding AAC using media-libs/fdk-aac.
fribidi	Enable unicode bidirectional algorithm support via dev-libs/fribidi.
nvenc	Adds support for NVIDIA Encoder (NVENC) API for hardware accelerated encoding on NVIDIA cards.
opus	Adds support for the Opus codec via media-libs/opus.
twolame	Enable TwoLAME support via media-sound/twolame, an optimised MPEG Audio Layer 2 (MP2) encoder.
vpx	Enable WebM VP8 Codec SDK support via media-libs/libvpx.
x265	Enables HEVC support with media-libs/x265.

babl

cpu_flags_x86_f16c	Take advantage of CPU feature f16c

cal3d

16bit-indices	Enables use of 16bit indices

chromaprint

tools	Build and install fpcalc and fpcollect tools

clutter

egl	Enable EGL backend.
gtk	Use gdk-pixbuf from x11-libs/gtk+ as image rendering backend

cogl

gles2	Enable OpenGL ES 2.0 support
kms	Enable KMS support.
pango	Build cogl-pango library for x11-libs/pango integration

coin

simage	Texture loading via media-libs/simage library

devil

allegro	Add support for Allegro
nvtt	Add support for media-gfx/nvidia-texture-tools

elementary

quicklaunch	Enable quick-launch support

esdl

image	Enable image support

faad2

digitalradio	Digital Radio Mondiale (warning: disables other decoders)

flickcurl

raptor	Use media-libs/raptor for proper RDF serializing

fontconfig-infinality

nyx	Additional style using croscorefonts

freetype

adobe-cff	Use Adobe CFF as default font-renderer
bindist	Disable ClearType support (see http://freetype.org/patents.html)
bzip2	Support bzip2 compressed PCF fonts.
cleartype_hinting	New bytecode hinting mode for TrueType fonts that activates subpixel hinting (a.k.a. ClearType hinting) by default
fontforge	Install internal headers required for TrueType debugger in media-gfx/fontforge (built with USE=truetype-debugger)
harfbuzz	Use media-libs/harfbuzz for auto-hinting OpenType fonts. WARNING: may trigger circular dependencies!
infinality	Enable infinality options for improved LCD filtering
utils	Install utilities and examples from ft2demos

freeverb3

audacious	Build Audacious plugin
forcefpu	Disable assembly code
plugdouble	Build plugins in double precision mode (default is float)

ganv

fdgl	Use experimental force-directed graph layout

gd

webp	Enable support for the webp format

gegl

lensfun	Enable support for media-libs/lensfun.
umfpack	Enable sparse solving via sci-libs/umfpack.
webp	Enable support for media-libs/libwebp

giflib

rle	Build converters for RLE format (utah raster toolkit)

gmtk

dconf	Enable support for gnome-base/dconf

grilo

network	Enable network access for media discovery using net-libs/libsoup
playlist	Enable support for playlists through dev-libs/totem-pl-parser

gst-plugins-bad

bzip2	Enable bzip2 encoder/decoder plugin
egl	Enable EGL support
gles2	Enable GLES2 support

gst-plugins-base

ivorbis	Enable integer based vorbis decoder
pango	Enable pango GStreamer plugin

gstreamer

orc	Disable some PaX memory protections to allow plugins that use dev-lang/orc for runtime optimization to be used on hardened PaX systems
unwind	Enable sys-libs/libunwind usage for better backtrace support in leaks tracer module

harfbuzz

glib	Compile with GLib Unicode support
graphite	Use graphite to render complex non-Roman writing systems

jbig2enc

webp	Add support for WEBP image format

leptonica

utils	Install command-line utilities
webp	Adds support for the WebP image format

libafterimage

shaping	Use MIT shaped X windows extention.
shm	Use MIT shared memory extention for X image transfer.

libass

harfbuzz	Enables OpenType shaping via media-libs/harfbuzz.

libbdplus

aacs	Add support for decryption of AACS

libbluray

aacs	Add support for decryption of AACS
bdplus	Use media-libs/libbdplus for BD+ decryption
java	Add support for BD-J
udf	Add UDF (Universal Disk Format) support
utils	Install command-line utilities and examples

libcanberra

alsa	Enables ALSA sound driver.
gstreamer	Enables gstreamer sound driver. Not useful when alsa or pulseaudio is available.
gtk	Enables building of gtk+ helper library, gtk+ runtime sound effects and the canberra-gtk-play utility. To enable the gtk+ sound effects add canberra-gtk-module to the colon separated list of modules in the GTK_MODULES environment variable.
gtk3	Enables building of gtk+3 helper library, gtk+3 runtime sound effects and the canberra-gtk-play utility. To enable the gtk+3 sound effects add canberra-gtk-module to the colon separated list of modules in the GTK_MODULES environment variable.
pulseaudio	Enables PulseAudio sound driver that should be able to support positional event sounds. This is the preferred choice for best sound events experience and picked by default if compiled in and possible to use at runtime.
sound	Install x11-themes/sound-theme-freedesktop to get sounds on Gnome and Xfce.
tdb	Enables Trivial Database support for caching purposes.

libextractor

apparmor	Enable apparmor support using sys-libs/libapparmor
archive	Enable archive support using app-arch/libarchive
gsf	Enable OLE2 (MS Office) plug-in support using gnome-extra/libgsf
magic	Enable magic support using sys-apps/file
midi	Enable MIDI support through media-libs/libsmf

libffado

qt4	Install qt4-based mixer frontend
test-programs	Install standalone test programs

libggi

vis	Enables sparc vis support for libggi

libgphoto2

serial	Enable serial port support

libgpod

gtk	Enable ArtworkDB support

libgroove

chromaprint	Enable audio fingerprinting using media-libs/chromaprint.
loudness	Enable loudness detection according to the EBU R128 standard using media-libs/libebur128.
sound	Enable audio playing.

liblastfm

fingerprint	Build the lastfm-fingerprint library

libmp4v2

utils	Install command-line utilities

libmypaint

gegl	Add support for media-libs/gegl

libomxil-bellagio

audioeffects	enable audio volume/mixer effects components
clocksrc	enable clock component
videoscheduler	enable xvideosink video scheduler

libopenglrecorder

openh264	Enable H.264 support using media-libs/openh264
vpx	Enable VP8/VP9 codec support via media-libs/libvpx

libpagemaker

tools	Build command line file format conversion tools

libpng

apng	support unofficial APNG (Animated PNG) spec

libpostproc

pic	Force shared libraries to be built as PIC (this is slower).

libquicktime

schroedinger	Enable Dirac video support (an advanced royalty-free video compression format) via libschroedinger (high-speed implementation in C of the Dirac codec)

libraw

demosaic	Enable support for external interpolation algorithms

libsdl

joystick	Control joystick support (disable at your own risk)
sound	Control audio support (disable at your own risk)
tslib	Build with tslib support for touchscreen devices
video	Control video support (disable at your own risk)

libsdl2

fusionsound	use FusionSound audio driver
gles	include OpenGL ES support
haptic	Enable the haptic (force feedback) subsystem
joystick	Control joystick support (disable at your own risk)
sound	Control audio support (disable at your own risk)
tslib	Build with tslib support for touchscreen devices
video	Control video support (disable at your own risk)

libvisio

tools	Build conversion tools

libvpx

highbitdepth	Enable 10 and 12 bit support for VP9.
postproc	Enable additional post processing filters
svc	Enable spatial-svc support (experimental)

libwebp

experimental	Build with -DWEBP_EXPERIMENTAL_FEATURES
swap-16bit-csp	Enable byte swapping for 16 bit colorspace

libyami

dmabuf	Enable dma_buf buffer sharing.
egl	Enable EGL support.
md5	Add support for generating md5 sums for each frame.
v4l	Add support for V4L2 hardware codecs.

libzmf

tools	Build conversion tools

lilv

dyn-manifest	Add LV2 Dynamic Manifest support. See http://lv2plug.in/ns/ext/dynmanifest/

lv2

plugins	Enables examples plugins.

lvtk

gtk2	Enable x11-libs/gtk+:2 based GUI support
tools	Compile and install ttl2c tool

mediastreamer

amr	Use of AMR Narrow Band codec plugin
filters	Enable compilation of filters
g726	Support g726 codec
g729	Use g726 codec plugin
ilbc	Use of iLBC (RFC3951) codec plugin
ntp-timestamp	Turn on NTP timestamping on received packet
opus	Enable opus codec support
ortp	Enable usage of net-libs/ortp
pcap	Enable usage of net-libs/libpcap
silk	Use silk (skype protocol) codec plugin
video	Enable video support

mesa

bindist	Disable patent-encumbered ARB_texture_float, EXT_texture_shared_exponent, and EXT_packed_float extensions.
classic	Build drivers based on the classic architecture.
d3d9	Enable Direct 3D9 API through Nine state tracker. Can be used together with patched wine.
dri3	Enable DRI3 support.
egl	Enable EGL support.
gallium	Build drivers based on Gallium3D, the new architecture for 3D graphics drivers.
gbm	Enable the Graphics Buffer Manager for EGL on KMS.
gles1	Enable GLESv1 support.
gles2	Enable GLESv2 support.
llvm	Enable LLVM backend for Gallium3D.
opencl	Enable the Clover Gallium OpenCL state tracker.
openmax	Enable OpenMAX video decode/encode acceleration for Gallium3D.
osmesa	Build the Mesa library for off-screen rendering.
pax_kernel	Enable if the user plans to run the package under a pax enabled hardened kernel
pic	disable optimized assembly code that is not PIC friendly
unwind	Add support for stack trace unwinding and function name resolution
valgrind	Compile in valgrind memory hints
vdpau	Enable the VDPAU acceleration interface for the Gallium3D Video Layer.
vulkan	Enable Vulkan drivers
wayland	Enable support for dev-libs/wayland
xa	Enable the XA (X Acceleration) API for Gallium3D.
xvmc	Enable the XvMC acceleration interface for the Gallium3D Video Layer.

mlt

compressed-lumas	Compress the luma files in png.
frei0r	Build the module for media-plugins/frei0r-plugins
kdenlive	Build support for kde-apps/kdenlive
lua	Build SWIG bindings for Lua
melt	Build the melt commandline tool
opencv	Build motion tracking module using media-libs/opencv
python	Build SWIG bindings for Python
rtaudio	Builds rtaudio consumer for native audio support on multiple platforms.
ruby	Build SWIG bindings for Ruby

netpbm

rle	Build converters for the RLE format (utah raster toolkit)

opencolorio

pdf	Install extra documentation in PDF format

opencv

contrib	Install user contributed scripts from opencv_contrib (Experimental!)
contrib_cvv	CVV module requires Qt5
contrib_hdf	HDF module requires sci-libs/hdf5
contrib_sfm	SFM module requires eigen, gflags, and glog
contrib_xfeatures2d	Enables xfeatures2d and autodownload of samples in contrib
cuda	Enable NVIDIA Cuda computations support (Experimental!)
eigen	Enable usage of dev-cpp/eigen for computations
gdal	Enable support for sci-libs/gdal library
gflags	Use Google's C++ argument parsing library
glog	Use Google's C++ loggin library
ipp	Enable Intel Integrated Primitive support
opencl	Add support for OpenCL
tesseract	Use Google's OCR Engine
testprograms	Build and install programs for testing OpenCV (performance)
vtk	Build new 3D visualization module viz based on sci-libs/vtk
webp	Enable support for webp image format

openh264

plugin	Install the Gecko Media Plugin (GMP) for use with Mozilla packages
utils	Install the CLI encoder and decoder utilities

openimageio

colorio	Use media-libs/opencolorio
cpu_flags_x86_avx512f	SIMD Optimization
cpu_flags_x86_f16c	SIMD Optimization
field3d	Use media-libs/Field3D
opencv	Use media-libs/opencv
ptex	Use media-libs/ptex
tbb	Use dev-cpp/tbb

opensubdiv

cuda	Enable NVIDIA CUDA Toolkit support through dev-util/nvidia-cuda-toolkit.
opencl	Enable OpenCL support through virtual/opencl.
ptex	Adds support for faster per-face texture mapping through media-libs/ptex.
tbb	Enable multithreading with the Intel Threads Building Blocks through dev-cpp/tbb.

opus

ambisonics	Enable ambisonics support (experimental).
custom-modes	Build with custom-modes.

opusfile

fixed-point	Enable fixed-point arithmetic operations
float	Enable floating point arithmetic operations
http	Enable http connections

osl

partio	Use media-libs/partio

phonon

designer	Install plugin for dev-qt/designer
vlc	Install VLC Phonon backend

phonon-gstreamer

network	Enable network streaming support via libsoup

portmidi

test-programs	Install various example programs

qtav

gui	Build a video player gui

quvi

json	Enable support for JSON output

raptor

json	Enable support for JSON parsing

raspberrypi-userland-bin

hardfp	Use armv6 hardfp ABI

sdif

ftruncate	Enables usage of ftruncate v. truncate

sdl-image

webp	support loading WEBP images

sdl-mixer

fluidsynth	Use media-sound/fluidsynth for MIDI support
midi	basic support for MIDI files
mod	basic support for MOD files
playtools	Install playwave and playmus tools (useful for testing)
smpeg	Use media-libs/smpeg for MP3 support
wav	support WAVE files

sdl-sound

physfs	Enable physfs support

sdl2-image

webp	support loading WEBP images

sdl2-mixer

fluidsynth	Use media-sound/fluidsynth for MIDI support
midi	basic support for MIDI files
mod	basic support for MOD files
playtools	Install playwave and playmus tools (useful for testing)
smpeg	Use media-libs/smpeg for MP3 support
tremor	enable OGG Vorbis music via libtremor
wav	support WAVE files

sge

image	enable sdl-image support

spandsp

fixed-point	Enable fixed point support

speex

utils	Enables speex commandline utilities (speexenc, speexdec).
vbr	Enable VBR support.

svgalib

kernel-helper	Build the helper kernel module

taglib

boost	Use dev-libs/boost instead of GCC built-ins

tremor

low-accuracy	enable 32bit only multiply operations

vigra

valgrind	Enable valgrind in make check

vips

fits	Enable support for the FITS image format through sci-libs/cfitsio
matio	Enable support for reading images from Matlab files through sci-libs/matio

waffle

egl	Enable EGL support
gbm	Enable support for the Generic Buffer Manager (gbm)
wayland	Enable Wayland support

x264

10bit	Set output bit depth to 10, this may not be compatible with all decoders
interlaced	enable interlaced encoding support, this can decrease encoding speed by up to 2%
opencl	Add support for OpenCL.
pic	disable optimized assembly code that is not PIC friendly

x265

10bit	Add support for producing 10bits HEVC.
12bit	Add support for producing 12bits HEVC.
numa	Build with support for NUMA nodes.
pic	Disable optimized assembly code that is not PIC friendly
power8	Enable support for Power 8 assembly optimizations.

xine-lib

bluray	Enable playback of Blu-ray filesystems using media-libs/libbluray
dxr3	Enable support for DXR3 mpeg acceleration cards.
flac	Build the media-libs/flac based FLAC demuxer and decoder. This flag is not needed for playing FLAC content, neither standalone nor in Ogg container (OggFLAC), but might have better support for exotic features like 24-bit samples or 96kHz sample rates.
fusionsound	Enable support for the Fusion audio sub system
gtk	Build the gdkpixbuf-based image decoder plugin.
imagemagick	Build the ImageMagick-based image decoder plugin.
mad	Build the media-libs/libmad based mp3 decoder. This mp3 decoder has superior support compared to the one coming from FFmpeg that is used as a fallback. If you experience any bad behaviour with mp3 files (skipping, distorted sound) make sure you enabled this USE flag.
mmap	Use mmap() function while reading file from local disks. Using mmap() will use more virtual memory space, but leaves to the Kernel the task of caching the file's data. mmap() access should be faster, but might misbehave if the device where the file resides in is removed during playback.
truetype	Use media-libs/freetype for font rendering and media-libs/fontconfig for font discovery. Enabling this USE flag will allow OSD (such as subtitles) to use more advanced font and to more easily select which font to use. The support for TrueType fonts in xine-lib is still experimental, and might not be as good looking as the bitmap fonts used with this USE flag disabled.
vdr	Build the VDR plugin
vidix	Enable support for vidix video output.
vis	Adds support for SIMD optimizations for UltraSPARC processors.
vpx	Enable VP8 codec support via media-libs/libvpx.
xvmc	Enable support for XVideo Motion Compensation (accelerated mpeg playback).

xvid

pic	disable optimized assembly code that is not PIC friendly

media-plugins

audacious-plugins

adplug	Build with AdPlug (Adlib sound card emulation) support
ampache	Support controlling audacious via www-apps/ampache
aosd	Enable support for Audacious OSD
bs2b	Enable Bauer Bauer stereophonic-to-binaural headphone filter
cue	Support CUE sheets using the libcue library
fluidsynth	Support FluidSynth as MIDI synth backend
gme	Support various gaming console music formats
gtk3	Link against version 3 of the GIMP Toolkit instead of version 2 (x11-libs/gtk+)
hotkeys	Enable support for controlling via hotkeys
http	Support HTTP streams through neon
scrobbler	Build with scrobbler/LastFM submission support
sid	Build with SID (Commodore 64 Audio) support
soxr	Build with SoX Resampler support
speedpitch	Enable speed/pitch effects

calf

experimental	Enable experimental features/plugins
lv2	Add support for Ladspa V2

frei0r-plugins

facedetect	Enables building of facedetect plugin, which depends on media-libs/opencv
scale0tilt	Enables building of scale0tilt and vectorscope plugins, which depend on media-libs/gavl

gkrellmpc

threads	Use separate thread to init connection (unsafe)

grilo-plugins

chromaprint	Enable Chromaprint support
daap	Enable dmap support through net-libs/libdmapsharing
flickr	Enable Flickr support
freebox	Build support for viewing TV channels using Freebox
gnome-online-accounts	Enable net-libs/gnome-online-accounts support
subtitles	Enables support for subtitle from OpenSubtitles
thetvdb	Build support for thetvdb.com
tracker	Build support for content discovery using the app-misc/tracker indexer
vimeo	Build support for Vimeo content discovery using net-libs/libsoup and dev-libs/libgcrypt
youtube	Build support for YouTube content discovery using dev-libs/libgdata

gst-plugins-gl

libvisual	Enable visualization effects via media-libs/libvisual

gst-plugins-meta

http	Enable http streaming via net-libs/libsoup
libvisual	Enable visualization effects via media-libs/libvisual
opus	Enable Opus audio codec support
vpx	Enables vp8 codec support using libvpx, required to play some HTML5 videos

gst-plugins-vaapi

drm	Enable DRM renderer
egl	Enable EGL support

hexter

gtk2	Enable x11-libs/gtk+:2 based GUI

imlib2_loaders

eet	Enable Eet image loader
xcf	Enable XCF image loader

kipi-plugins

flashexport	Build the flash export plugin
mediawiki	Build the mediawiki export plugin
remotestorage	Build plugin for remote storage using network protocols such as FTP, SSH, SAMBA via kde-frameworks/kio
vkontakte	Build plugin for vkontakte.ru

mediastreamer-ilbc

20ms-frames	enable 20ms frame size (default is 30ms). Some VOIP providers such as Gizmo5 (aka Sipphone) require the codec to be compiled with the 30ms setting.

mythplugins

cdr	Allows MythMusic to burn CD-Rs
exif	Allows MythGallery to read EXIF data from photos
fftw	Adds visual effects to MythMusic when playing back music
hls	HTTP Live Streaming support
mytharchive	Allows you to archive recorded content to CD or DVD
mythbrowser	Adds a web browser within MythTV
mythgallery	Adds a picture viewing gallery within MythTV
mythgame	Adds a frontend to various ROM emulators within MythTV
mythmusic	Adds the ability for MythTV to act as a music player
mythnetvision	Adds the ability to view netvision devices within MythTV
mythnews	Adds a news viewer within MythTV
mythweather	Adds weather information within MythTV
mythzoneminder	Adds support for zoneminder (requires a server with the appropriate mythtv daemon somewhere on the network).
raw	Allows MythGallery to view photos saved in RAW format

vdr-burn

dvdarchive	DMH DVD - Archive

vdr-epgsearch

conflictcheckonly	ToDo
epgsearchonly	ToDo
quicksearch	ToDo
tre	Add support for unlimited fuzzy searching with help of dev-libs/tre library

vdr-graphtft

graphtft-fe	Install external x11 remote frontend
theme_avp	graphTFT Alien vs. Predato theme
theme_deepblue	graphTFT default theme
theme_deeppurple	graphTFT Deep Purple theme
theme_poetter	graphTFT Poetter theme
touchscreen	Enable Touchscreen support

vdr-music

graphtft	Enable support for media-plugins/vdr-graphtft

vdr-pvr350

yaepg	Enables full support for the output format of vdr-yaepg

vdr-streamdev

client	Compile the VDR plugin vdr-streamdev-client that acts like a dvb-budget card
server	Compile the VDR plugin vdr-streamdev-server that allows remote systems to access the DVB cards used for the local VDR

vdr-text2skin

contrib	Install user contributed scripts

vdr-vdrmanager

stream	Add support for streaming Video to Android client

vdr-weatherng

dxr3	enables lower osd color depth for dxr3 cards

vdr-xine

yaepg	Enables support for the plugin vdr-yaepg (showing scaled video besides OSD)

vdr-xineliboutput

bluray	Enable BluRay metadata support through media-libs/libbluray
cec	Enable CEC support through dev-libs/libcec
libextractor	Use media-libs/libextractor to gather files' metadata in media-player
vdr	Compile the vdr output plugin to use local or remote xine as output
xine	Compile the xine input plugin for displaying vdr video and OSD

media-radio

ax25-tools

X	Enable some X based configuration tools.

fldigi

hamlib	Enables support by the Hamlib amateur radio rig control library to get/set frequency and mode of the ham radio in use

tucnak

hamlib	Enables support by the Hamlib amateur radio rig control library to get/set frequency and mode of the ham radio

tucnak2

ftdi	Enable support for FTDI USB chips
hamlib	Enables support by the Hamlib amateur radio rig control library to get/set frequency and mode of the ham radio

unixcw

ncurses	Enables building the curses based morse code tutor program 'cwcp'.

xastir

festival	Enable text to speech synthesizer
gdal	Support for some further map formats
geotiff	Install geotiff support. Allows using USGS DRG topo maps or other types of geotiff mapes/images

media-sound

abcde

id3tag	Support ID3, ID3v2 tagging of audio files
mac	Enable support for Monkey's Audio files
normalize	Add support for normalizing audio file volume levels
opus	Support opus encoding using opusenc
replaygain	Support for Replay Gain metadata, for relative volume adjustment

abcm2ps

pango	Use the pango library to render fonts with non-latin characters

alsa-utils

bat	install basic audio tester (BAT) util
libsamplerate	install utils that use libsamplerate (e.g. alsaloop)
ncurses	install utils that use ncurses (e.g. alsamixer)

alsaplayer

id3tag	Enables ID3 tagging with id3tag library

amarok

embedded	Use libmysqld, MySQL embedded server library. Try disabling this if you encounter -PIC related in amarok, it will make amarok rely only on standalone MySQL server.
lastfm	Enable Last.fm streaming services support through media-libs/liblastfm
mp3tunes	Enable mp3tunes integration
mtp	Enable support for libMTP (Plays4Sure) devices access through libmtp
ofa	Use media-libs/libofa to compute MusicDNS acoustic fingerprints (used by MusicBrainz)
utils	Build the utils - old media-sound/amarok-utils

amsynth

dssi	Enable support for DSSI Soft Synth Interface

aqualung

ifp	Enable support for iRiver iFP portable audio players
lua	Enable support for programmable title formatting with dev-lang/lua
mac	Enable support for decoding Monkey's Audio files
podcast	Enable podcast support
systray	Enable system tray support

ardour

lv2	Add support for Ladspa V2

ario

audioscrobbler	Enable song tracking via last.fm
idle	Enable experimental support for MPD's idle command to reduce bandwidth and cpu usage, requires MPD 0.14

asunder

mac	Support for creation of Monkey's Audio files (APE)
opus	Support for creation of Opus files

audacious

gtk3	Link against version 3 of the GIMP Toolkit instead of version 2 (x11-libs/gtk+)

audacity

id3tag	Enables ID3 tagging with id3tag library
lv2	Add support for Ladspa V2
midi	Enables MIDI support
portmixer	Enable the internal portmixer feature
sbsms	Enables sbsms library support for slower, more accurate pitch and tempo changing
soundtouch	Enables soundtouch library support for pitch and tempo changing
twolame	Enables twolame support (MPEG Audio Layer 2 encoder)
vamp	Enables vamp plugins support (Audio analysing plugins)
vst	Enable VST plugin support

beets

badfiles	Validate MP3 & FLAC files
bpd	Enable support for media-sound/mpd server emulation
chroma	Enable support for acoustic fingerprinting plugin using media-libs/chromaprint
convert	Enable support for the convert plugin which makes it possible to transcode files
discogs	Enable support for the discogs API plugin
lastgenre	Enable support for importing music genres from last.fm tags
lastimport	Enable support for importing your last.fm playcounts
mpdstats	Enable support for collecting statistic about listening habits from media-sound/mpd
opus	Enable opus support in gstreamer-based replaygain
replaygain	Enable support for Replay Gain metadata calculation during import
thumbnails	Generate thumbnails for albums
web	Enable embedded webserver support through dev-python/flask

bluez-alsa

hcitop	Enable top-like monitoring tool for HCI

cantata

cdio	Use dev-libs/libcdio-paranoia for CD support (instead of cdparanoia)
http-server	Enable internal HTTP server to play non-MPD files
replaygain	Enable ReplayGain support, for relative volume adjustments
streaming	Enable playback of MPD HTTP streams using LibVLC (media-video/vlc)

clementine

box	Enable filesharing via Box.com
dropbox	Enable Dropbox support
googledrive	Enable Google Drive support
lastfm	Use liblastfm for fetching song info, scrobbling and radio streams
moodbar	Enable moodbar support
projectm	Build with ProjectM visualization
seafile	Enable support for seafile: a file sync service
skydrive	Enable Skydrive support
wiimote	Enable support for Wii remote

cmus

cdio	use libcdio for CD support
cue	enable CUE sheet parsing
discid	enable reading the ID of the inserted CD
opus	enable support for media-libs/opusfile
pidgin	install support script for net-im/pidgin
tremor	use libivorbis from media-libs/tremor instead of media-libs/libvorbis

csound

beats	Build the beats score frontend
chua	Build the chua opcodes
csoundac	Build the CsoundAC extension module
double-precision	Use double-precision floating point for audio samples
dssi	Build the DSSI opcodes
fluidsynth	Build the fluidsynth opcodes
image	Build the image opcodes
keyboard	Build Virtual MIDI keyboard
linear	Build the linear algebra Opcodes
luajit	Use the lua just-in-time compiler dev-lang/luajit instead of dev-lang/lua
portmidi	Build the PortMIDI I/O module
samples	Install the HRTF datafiles for use with hrtfmove, hrtfmove2, hrtfstat, hrtfearly, and hrtfreverb
score	Build the alternative score parser
stk	Build the stk opcodes
tcl	Build the tcl interface and clients
utils	Build stand-alone executables for utilities that can also be used via `csound -U`
websocket	Build the websocket opcode

darkice

aacplus	AAC+ encoding via media-libs/libaacplus
opus	Enable Opus audio codec support
twolame	Build with twolame support

denemo

fluidsynth	Enable Fluidsynth MIDI software synthesis
portmidi	Enable support for the portmidi backend

dir2ogg

mac	Add support for decoding Monkey's Audio files
wma	Add support for wma files through mplayer

drumstick

fluidsynth	Enable support for media-sound/fluidsynth

easytag

opus	Enable support for media-libs/opus and media-libs/opusfile (opus audio codec)

ecasound

lv2	Add support for Ladspa V2
oil	Use dev-libs/liboil for inner loop optimizations

fapg

xspf	Enable support for saving XSPF playlists.

forked-daapd

itunes	Enable support for iTunes library XML
lastfm	Enable LastFM scrobbling support
mpd	Enable streaming to mpd

gimmix

cover	Enable cover art fetching
lyrics	Enable lyric fetching

gmpc

unique	Enable single instance support using dev-libs/libunique
xspf	Enable support for reading and saving XSPF playlists

gmusicbrowser

extras	Install some extra deps for plugins (ex. Titlebar)

gogglesmm

opus	Enable support for opus codec

herrie

http	Enable http streaming
xspf	Enable support for reading and saving XSPF playlists

hydrogen

archive	Use libarchive instead of libtar
portmidi	Add portmidi support

jack-audio-connection-kit

coreaudio	Build the CoreAudio driver on Mac OS X systems
cpudetection	Enables runtime cpudetection
pam	Add basic realtime configuration via sys-auth/realtime-base

jack2

celt	Support CELT low delay audio codec (media-libs/celt)
classic	Enable building of jackd
opus	Support media-libs/opus
pam	Add basic realtime configuration via sys-auth/realtime-base

jalv

gtk2	Adds support for GTK+2 in addition to GTK+3 controlled by the gtk useflag.
gtkmm	Adds support for dev-cpp/gtkmm: C++ interface for GTK+2

kid3

acoustid	Enable support for acoustic fingerprinting plugin using (media-libs/chromaprint)

klick

rubberband	Enable rubberband support

lame

frontend	Build and install the 'lame' executable frontend to lame libraries.
mp3rtp	Build the mp3-to-RTP streaming utility. **UNSUPPORTED**

lilypond

guile2	Enable experimental support for Guile 2

linuxsampler

lv2	Add support for Ladspa V2

lmms

fluidsynth	Enables Fluidsynth MIDI software synthesis plugin.
libgig	Enables GIG player plugin.
soundio	Enalbes libsoundio support.
stk	Enables STK Mallet plugin.
vst	Enables the VeSTige plugin to run VST plugins through Wine.

lyvi

mpris	Enable MPRIS support

mangler

espeak	Text to speech engine
g15	Logitech g15 lcd support
opus	Codec specialized for speech over the internet

mixxx

hid	Enable HID controller support
shout	Enable broadcasting support via media-libs/libshout

moc

cache	Enable tags caching support
magic	Use libmagic to determine mimetypes
sid	Build with SID (Commodore 64 Audio) support
tremor	Build vorbis support using an integer implementation of the vorbis library (media-libs/tremor)

mp3blaster

sid	Build with SID (Commodore 64 Audio) support

mp3splt-gtk

audacious	Include media-sound/audacious support

mpd

adplug	Enable the AdPlug decoder plugin
cdio	Use libcdio for ISO9660 parsing support
curl	Support for web stream listening
eventfd	Use the eventfd function in MPD's event loop
faad	Use external faad library for AAC decoding
fifo	Support writing audio to a FIFO
fluidsynth	Enables Fluidsynth MIDI software synthesis (discouraged)
glib	Enable GLib usage
gme	Enables support for media-libs/game-music-emu for playing various video game music formats.
id3tag	Support for ID3 tags
inotify	Use the Linux kernel inotify subsystem to notice changes to mpd music library
lame	Support for MP3 streaming via Icecast2
libmpdclient	Enable support for remote mpd databases
libsoxr	Enable the libsoxr resampler
mpg123	Enable support for mp3 decoding over media-sound/mpg123
network	Enables network streaming support
nfs	Enable support for the Network File System
opus	Enable Opus codec support
pipe	Support writing audio to a pipe
recorder	Enables output plugin for recording radio streams
sid	Build with SID (Commodore 64 Audio) support
signalfd	Use the signalfd function in MPD's event loop
soundcloud	Build plugin to access soundcloud
systemd	Enable support for systemd socket activation
twolame	Support twolame MPEG-2 encoding
webdav	Enable using music from a WebDAV share
wildmidi	Enable MIDI support via wildmidi
zip	Support for ZIP files

mpfc

wav	Enable wav audio codec support

mpg123

int-quality	Use rounding instead of fast truncation for integer output, where possible

mumble

g15	Enable support for the Logitech G15 LCD (and compatible devices).
speech	Enable text-to-speech support in Mumble.

murmur

ice	Use dev-libs/Ice to enable remote control capabilities.

musescore

portmidi	Enable support for building against media-libs/portmidi

ncmpc

artist-screen	Enable artist screen
chat-screen	Enable the chat screen
colors	Enable color support
help-screen	Enable the help screen
key-screen	Enable key editor screen
lyrics-screen	Enable lyrics screen
mouse	Enable curses getmouse support
search-screen	Enable search screen
song-screen	Enable song viewer screen

ncmpcpp

clock	Enable clock screen
outputs	Enable outputs screen
visualizer	Enable visualizer screen with sound wave/frequency spectrum modes

patchage

jack-dbus	Use Jack via D-Bus instead of libjack
session	Include experimental Jack session management (save/restore) support

pithos

appindicator	Enable usage of appindicator to export menu options in to unity
keybinder	Use keybinder to enable global key bindings

pms

regex	Enable regular expression searches

podcatcher

bittorrent	Enable support for bittorrent downloads

potamus

opus	Adds support for the Opus codec.

pragha

glyr	Enable music metadata searchengine support using media-libs/glyr
grilo	Play songs on DLNA servers using media-libs/grilo
keybinder	Enable shortcut support using dev-libs/keybinder
lastfm	Enable last.fm support using media-libs/libclastfm
peas	Enable various plugins that will pull in dev-libs/libpeas as a dependency
playlist	Enable enhanced playlist support using dev-libs/totem-pl-parser
rygel	Share music on DLNA using net-misc/rygel
soup	Search metadata on AcoustID and radios on TuneIn using net-libs/libsoup

puddletag

acoustid	Use media-libs/chromaprint for acoustic fingerprinting
cover	Enables editing of FLAC cover art
musicbrainz	Enables support for musicbrainz, needs dev-python/python-musicbrainz
quodlibet	Enables support for editing media-sound/quodlibet databases

pulseaudio

X	Build the X11 publish module to export PulseAudio information through X11 protocol for clients to make use. Don't enable this flag if you want to use a system wide instance. If unsure, enable this flag.
alsa-plugin	Request installing media-plugins/alsa-plugins with PulseAudio plugin enabled. This ensures that clients supporting ALSA only will use PulseAudio.
asyncns	Use libasyncns for asynchronous name resolution.
doc	Build the doxygen-described API documentation.
equalizer	Enable the equalizer module (requires sci-libs/fftw).
gdbm	Use sys-libs/gdbm to store PulseAudio databases. Recommended for desktop usage. This flag causes the whole package to be licensed under GPL-2 or later.
glib	Add support to dev-libs/glib-based mainloop for the libpulse client library, to allow using libpulse on glib-based programs.
gnome	Use GConf to store user preferences on streams and so on. Don't enable this flag if you want to use a system wide instance. If unsure, enable this flag.
native-headset	Build with native HSP backend for bluez 5.
ofono-headset	Build with oFono HFP backend for bluez 5, requires net-misc/ofono.
oss	Enable OSS sink/source (output/input). Deprecated, upstream does not support this on systems where other sink/source systems are available (i.e.: Linux). The padsp wrapper is now always build if the system supports OSS at all.
realtime	Makes PulseAudio use RealtimeKit (sys-auth/rtkit) to get real-time priority while running.
ssl	Use dev-libs/openssl to provide support for RAOP (AirPort) streaming.
system-wide	Allow preparation and installation of the system-wide init script for PulseAudio. Since this support is only supported for embedded situations, do not enable without reading the upstream instructions at https://www.freedesktop.org/wiki/Software/PulseAudio/Documentation/User/WhatIsWrongWithSystemWide/ .
systemd	Build with sys-apps/systemd support to replace standalone ConsoleKit.
webrtc-aec	Uses the webrtc.org AudioProcessing library for enhancing VoIP calls greatly in applications that support it by performing acoustic echo cancellation, analog gain control, noise suppression and other processing.

qmidiarp

lv2	Enables Ladspa V2 plugins.

qmmp

analyzer	Enable visual analyzer
archive	Enable archiving plugin via app-arch/libarchive.
bs2b	Enable Bauer stereophonic-to-binaural headphone filter
cover	Enable album cover support
crossfade	Enable crossfade effect when switching tracks
cue	enable CUE sheet parsing
dbus	Enable DBus notifiications and MPRIS support
enca	Detects the character encoding automatically
game	Enable Game music support
gnome	Enable Gnome hotkey support (requires Qt5DBus)
lyrics	Fetch track lyrics from the web
midi	Enable midi support using wildmidi library
notifier	Enable qmmps' notifier system
opus	Enable the opus plugin
projectm	Enable projectm music visualization plugin
qsui	Enable QMMP simple UI
qtmedia	Enable playback via dev-qt/qtmultimedia
scrobbler	Enable audioscrobbler/last.fm support
shout	Enable shoutcast plug-in via media-libs/libshout.
sid	Build with SID (Commodore 64 Audio) support
soxr	Use the SoX resampling library
stereo	Enable stereo effect
tray	Build tray icon

qsampler

libgig	Enable libgig support for loading Gigasampler files and DLS (Downloadable Sounds) Level 1/2 files

qtractor

dssi	Enable support for DSSI Soft Synth Interface
rubberband	Enable support for in-place audio clip pitch-shifting through the rubberband library

qtscrobbler

cli	Build commandline client

quark

gnome	Provides tray-icon and enables gconf support

rhythmbox

daap	Build the local network music sharing plugin which uses the DAAP protocol using net-libs/libdmapsharing
visualizer	Enable support for visualizations using media-plugins/gst-plugins-libvisual
zeitgeist	Build the plugin to inject events to gnome-extra/zeitgeist

shntool

alac	Add support for Apple Lossless Audio Codec files
mac	Add support for Monkey's Audio files

snd

s7	Enable the s7 extension language (a version of Scheme)

sonata

lyrics	Support for lyrics fetching
trayicon	Enable support for trayicon

sonic-visualiser

id3tag	Enables ID3 tagging with id3tag library

soundconverter

opus	Enable Opus audio codec support

sox

amr	Enables Adaptive Multi-Rate Audio support
id3tag	Enables ID3 tagging with id3tag library
opus	Enables reading Ogg Opus files.
twolame	Enables twolame support (MPEG Audio Layer 2 encoder)

split2flac

enca	Try to guess the charset using enca
flake	Add support for Flake, alternative FLAC encoder
mac	Add support for Monkey's Audio files
replaygain	Support for Replay Gain metadata, for relative volume adjustment

spotify

pax_kernel	Triggers a paxmarking of the main Spotify binary

supercollider

emacs	Enable the SCEL user interface
gedit	Enable the SCED user interface
gpl3	Build GPL-3 licensed code (recommended)
server	Build with internal server
vim	Enable the SCVIM user interface
wiimote	Build sclang with Wii Remote support

teamspeak-server-bin

tsdns	Make use of TeamSpeak DNS.

tomahawk

hatchet	Enable support for the synchronisation through Hatchet
telepathy	Enable support for the real-time communication framework telepathy

traverso

lv2	Add support for Ladspa V2

tuxguitar

fluidsynth	Enables Fluidsynth MIDI software synthesis (with external sound fonts). JSA must be disabled in the plug-ins menu to use this.
lilypond	Exports the score in a lilypond compatible format.
pdf	Exports the score as a PDF file using dev-java/itext.
tray	Adds an icon to the tray that controls midi playback.

umurmur

shm	Enable shared memory support

vimpc

boost	Use boost instead of C++11 libraries

vorbis-tools

kate	Adds support for Ogg Kate subtitles via libkate.
ogg123	Build ogg123 player, needs libao and curl

wildmidi

player	Install the wildmidi player

xmms2

airplay	Support for airplay format
asf	Support for Monkey's Audio (APE) format with help of bundled libasf
fluidsynth	Enable fluidsynth support (MIDI)
gvfs	Transport for glibs virtual filesystem
ices	Icecast source output plugin
mac	Support for Monkey's Audio (APE) format with help of media-sound/mac
mlib-update	Enable building of xmms2-mlib-updater client
ofa	Support for Open Fingerprint Architecture (OFA)
opus	Enable Opus audio codec support
phonehome	This client sends anonymous usage-statistics to the xmms2
server	Build xmms2 player daemon (otherwise only clients are built)
sid	Support for C64 SID
valgrind	Run unit tests under valgrind.
vocoder	Phase vocoder effect plugin
xml	Enable support for various XML based playlists and sources: RSS, XSPF

xnoise

lastfm	Enable support for lastfm cover art fetching and scrobbling
lyrics	Enable support for lyrics fetching

xwax

alsa	Adds support for ALSA audio input/output.
cdda	Sets runtime dependencies to support decoding audio from a compact disc.
fallback	Sets runtime dependencies to support decoding "other" audio files.
jack	Adds support for audio input/output via the JACK Audio Connection Kit.
mp3	Sets runtime dependencies to support decoding MP3 audio.
oss	Adds support for OSS (open sound system) audio input/output.

yoshimi

lv2	Add support for Ladspa V2

media-tv

gentoo-vdr-scripts

nvram	Add support for using nvram-wakeup to set wakeup time in bios

kodi

airplay	enable AirPlay support
bluray	Enable playback of Blu-ray filesystems
cec	Enable support for HDMI-CEC devices via libcec
dvd	Enable optical (CD/DVD drive) support
gbm	Use the Graphics Buffer Manager for EGL on KMS.
gles	Enable support for GLES
libusb	Use virtual/libusb for usb device hotplug support. This flag should only be enabled if you're running a non-Linux kernel or you don't want to use sys-fs/udev.
lirc	Enable support for controlling Totem with a remote control using app-misc/lirc
nfs	Enable NFS client support
nonfree	Enable non-free components
sftp	Support browsing files over SFTP
system-ffmpeg	Use system ffmpeg instead of the bundled one
udev	Use sys-fs/udev rules to handle devices' permissions and hotplug support. Unless you know what you're doing do not disable this flag on Linux kernels. This is provided as an option for completeness.
webserver	Enable internal webserver
xslt	Enable XSLT support using dev-libs/libxslt

linuxtv-dvb-apps

alevt	Build videotext decoder

me-tv

http	Installation of Web-frontend

mythtv

alsa	Allows MythTV to directly output sound to ALSA devices, this is needed if you are using ALSA dmix or SPDIF. Note, you will have to physically type your device into the MythTV configuration since it will only give you /dev/dsp devices in the drop down.
altivec	Builds ffmpeg's codec libraries with altivec support.
autostart	Uses a custom autostart configuration gleaned from experience with MythTV since its early versions and discussed with other MythTV maintainers and users. Does not rely on KDE being installed like most methods do.
bluray	Pulls in libbluray for BluRay support.
cec	Allows you to control CEC enabled TVs via HDMI. Currently requires a USB based CEC -> HDMI injector between your TV and video card since no graphics drivers support CEC natively.
crystalhd	Allows you to utilize a Broadcom CrystalHD hardware based video decoder to improve the performance of video decode.
debug	Instructs Qt to use the 'debug' target instead of 'release' target. If your MythTV is crashing or you need a backtrace, you need to compile it with this option otherwise the debugging data is useless.
egl	Support EGL video output.
fftw	Support visualizations via sci-libs/fftw
hls	HTTP Live Streaming support
ieee1394	Allows MythTV to communicate and use Firewire enabled Cable boxes. These are typically found in the United States, where such support is required by law. This will also install Firewire test programs and external channel changers if the internal changer does not work.
jack	Allows MythTV to use JACK as your sound output device. You will have to manually configure the path to your JACK settings.
lcd	Tells MythTV that you have an instance of app-misc/lcdproc configured on your machine and it should output information such as current time, show name, episode name, etc to that LCD.
lirc	Adds LIRC support directly to MythTV allowing for built in control via a LIRC device.
mythlogserver	Enable support for syslog and file logging. Not used with systemd.
perl	Builds the perl bindings for MythTV. Allows you to write scripts in Perl to control your MythTV setup or communicate with it.
wrapper	Use Ubuntu mythtfrontend wrapper.
xmltv	Pulls in the media-tv/xmltv TV listing grabbers for users not using Schedules Direct.

tvbrowser

themes	Install extra theme packs

tvheadend

capmt	Enable support for capmt (dvbapi) protocol
constcw	Enable support for the constcw protocol
cwc	Enable support for the cwc (newcamd) protocol
ddci	Enable support for DDCI hardware
dvbcsa	Enable decryption of the DVB Common Scrambling Algorithm
dvben50221	Enable support for hardware CAM
hdhomerun	Enable support for the HDHomeRun device
imagecache	Enable support for image caching
iptv	Enable support for Internet Protocol TV
opus	Enable transcoding with the Opus audio codec
satip	Enable support for IP-based Satellite TV
timeshift	Enable TimeShift support
uriparser	Use dev-libs/uriparser
vpx	Enable transcoding with the VP8/VP9 video codecs
x264	Enable transcoding with the H.264 video codec
x265	Enable transcoding with the HEVC video codec
xmltv	Use media-tv/xmltv

v4l-dvb-saa716x

firmware	Install firmware

xmltv

ar	Argentina tv listing grabber
ch	Switzerland bluewin tv listing grabber
ch_search	Grabber for Switzerland
dk	Denmark tv listing grabber
dtvla	Latin America digital tv listing grabber
ee	Estonia tv listing grabber
es_laguiatv	Spain alternative grabber
es_miguiatv	Spain alternative grabber
eu_dotmedia	Grabber for Europe (xmltv.se / dotmedia)
eu_egon	Grabber for german speaking area (Egon zappt)
eu_epg	EPG grabber for some European countries.
fi	Finland tv listing grabber
fi_sv	Grabber for Finland (Swedish)
fr	France tv listing grabber
fr_kazer	France (Kazer) tv listing grabber
hr	Croatia tv listing grabber
huro	Hungarian tv listing grabber
il	Israel tv listing grabber
in	India tv listing grabber
is	Iceland tv listing grabber
it	Italy tv listing grabber
na_dd	North America tv listing grabber
na_dtv	North America Direct TV grabber
na_icons	option for na_dd to download icons
na_tvmedia	Grabber for North America (TVMedia)
nl	Netherlands tv listing grabber
no_gf	Norway Gfeed tv listing grabber
pt	Portugal tv listing grabber
pt_meo	Grabber for Portugal (MEO)
re	Reunion Island (France) tv listing grabber
sd_json	Grabber for schedulesDirect.org SD-JSON service (many countries)
se_swedb	Sweden tv listing grabber
se_tvzon	Sweden (tvzon.se) tv listing grabber
tr	Turkey (Digiturk) tv listing grabber
tv_check	enable GUI checking
tv_combiner	enable grabbers combiner
tv_pick_cgi	enable CGI support
uk_atlas	Fast UK and Ireland tv listing grabber
uk_bleb	Britain tv listing grabber
uk_rt	Britain alternative tv listing grabber
uk_tvguide	UK and Ireland tv listing grabber using TV Guide website
za	South Africa tv listing grabber
zz_sdjson	Grabber for schedulesDirect.org SD-JSON service (many countries)

media-video

aegisub

uchardet	Enable charset discovery via app-i18n/uchardet

aravis

X	Build the GTK+-based video viewer for aravis. This requires GStreamer and a few plugins but technically not the GST plugin for aravis.
gstreamer	Build the GStreamer plugin for aravis, but not the video viewer.

avidemux

nvenc	Adds support for NVIDIA Encoder (NVENC) API for hardware accelerated encoding on NVIDIA cards.

chaplin

transcode	Enable DVD ripping and transcoding

clive

clipboard	Support reading from X clipboard
pager	Support pager!?
password	Support password controlled sites

dcpomatic

alsa	Utilize alsa output of media-libs/rtaudio.
jack	Utilize jack output of media-libs/rtaudio.
pulseaudio	Utilize pulseaudio output of media-libs/rtaudio.

dv2sub

kino	install kino plugin

dvdrip

fping	Enables fping support for cluster rendering
subtitles	Enables support for subtitle ripping

ffdiaporama

openclipart	Support openclipart database
texturemate	Install extra backgrounds

ffmpeg

amr	Enables Adaptive Multi-Rate Audio support
amrenc	Enables Adaptive Multi-Rate Audio encoding support with media-libs/vo-amrwbenc.
appkit	Enables Apple AppKit framework
armv5te	Enables optimizations for armv5te processors.
armv6	Enables optimizations for armv6 processors.
armv6t2	Enables optimizations for armv6t2 processors.
armvfp	Enables VFP optimizations for ARM processors.
bluray	Enable playback of Blu-ray filesystems
bs2b	Enables media-libs/libbs2b based Bauer stereo-to-binaural filter.
cdio	Enables audio CD grabbing with dev-libs/libcdio.
celt	Adds Xiph CELT audio decoding support via media-libs/celt
chromaprint	Enables audio fingerprinting support with media-libs/chromaprint.
chromium	Builds libffmpeg.so to enable media playback in Chromium-based browsers like Opera and Vivaldi.
cpudetection	Enables runtime CPU detection (useful for bindist, compatibility on other CPUs)
ebur128	Enables EBU R128 loudness normalization filter via media-libs/libebur128
fdk	Use external fdk-aac library for AAC encoding
flite	Adds a text-to-speech filter based on app-accessibility/flite.
frei0r	Enable frei0r wrapping in libavfilter
fribidi	Enables fribidi support in the drawtext filter.
gcrypt	Enables gcrypt support: Needed for rtmp(t)e support if openssl, librtmp or gmp is not used.
gme	Enables support for media-libs/game-music-emu for playing various video game music formats.
gpl	Build GPL code. Should be enabled unless you require LGPL binaries.
hardcoded-tables	Use pre-calculated tables rather than calculating them on the fly.
iec61883	Support for FireWire DV/HDV input device using media-libs/libiec61883.
kvazaar	Enables media-libs/kvazaar based HEVC encoder.
libilbc	Enables iLBC de/encoding via media-libs/libilbc.
librtmp	Enables Real Time Messaging Protocol using librtmp (media-video/rtmpdump) in addition to FFmpeg's native implementation.
libsoxr	Enables audio resampling through media-libs/soxr.
libv4l	Uses media-libs/libv4l for video4linux instead of direct calls. Adds support for more devices via the userspace library.
mipsdspr1	Enables MIPS DSP ASE R1 optimizations.
mipsdspr2	Enables MIPS DSP ASE R2 optimizations.
mipsfpu	Enables floating point MIPS optimizations.
mmal	Enables Multi-Media Abstraction Layer (MMAL) decoding support: Available e.g. on the Raspberry Pi.
network	Enables network streaming support
nvenc	Adds support for NVIDIA Encoder (NVENC) API for hardware accelerated encoding on NVIDIA cards.
openh264	Enables H.264 encoding suppoprt via media-libs/openh264.
openssl	Enables dev-libs/openssl support. Adds support for encrypted network protocols (TLS/HTTPS).
opus	Adds (decoding) support for the Opus codec via media-libs/opus.
pic	Force shared libraries to be built as PIC (this is slower)
postproc	Build and install libpostproc.
rubberband	Adds time-stretching and pitch-shifting audio filter based on media-libs/rubberband.
schroedinger	Enable Dirac video support (an advanced royalty-free video compression format) via libschroedinger (high-speed implementation in C of the Dirac codec).
snappy	Enable app-arch/snappy support. Required for e.g. Vidvox Hap encoder.
sofalizer	Enables Sofalizer filter
ssh	Enable SSH/sftp support via net-libs/libssh.
twolame	Enables MP2 encoding via media-sound/twolame as an alternative to the internal encoder.
vpx	Enables vp8 codec support using libvpx: Decoding vp8 does not require this to be enabled but libvpx can also be used for decoding; encoding vp8 requires this useflag to be enabled though.
webp	Enables WebP encoding with media-libs/libwebp.
x265	Enables HEVC encoding with media-libs/x265.
zeromq	Enables net-libs/zeromq support with the zmq/azmq filters.
zimg	Enables media-libs/zimg based scale filter.
zvbi	Enables media-libs/zvbi based teletext decoder.

ffmpeg2theora

kate	Adds support for Ogg Kate subtitles via libkate.

gnome-mplayer

dconf	Enable support for gnome-base/dconf
gda	Enable support for gnome-extra/libgda

google2srt

html	Install HTML documentation

h264enc

ogm	Support for OGM container format

handbrake

fdk	Support for encoding AAC using media-libs/fdk-aac.
gstreamer	Support for the streaming media framework from media-libs/gstreamer.
gtk	Install the GTK UI, ghb.
libav-aac	Support for encoding AAC using media-video/libav's internal encoder.
x265	Support for encoding h265 using media-libs/x265.

kino

gpac	Enable GPAC support when exporting to 3GPP format

kmplayer

npp	Compile the npp backend that plays xembed style browser plugins.

libav

aac	Use external vo-aacenc library for AAC encoding
amr	Enable Adaptive Multi-Rate Audio support
armv5te	Enable optimizations for armv5te processors
armv6	Enable optimizations for armv6 processors
armv6t2	Enable optimizations for armv6t2 processors
armvfp	Enable VFP optimizations for ARM processors
bs2b	Enable media-libs/libbs2b based Bauer stereo-to-binaural audio filter
cdio	Enable audio CD grabbing with dev-libs/libcdio.
cpudetection	Enables runtime CPU detection (useful for bindist, compatibility on other CPUs).
faac	Use external faac library for AAC encoding
fdk	Use external fdk-aac library for AAC encoding and decoding
frei0r	Enable frei0r wrapping in libavfilter
gpl	Build all GPL licensed code. Without this flag set the package is build under LGPL license.
hardcoded-tables	Use pre-calculated tables rather than calculating them on the fly.
network	Enable network streaming support.
nvidia	Enable nvidia video codec hardware acceleration support.
openssl	Prefer dev-libs/openssl over net-libs/gnutls to provide SSL/TLS support (notice: the resulting binaries are unredistributable).
opus	Use the external opus library for encoding and decoding.
pic	Force shared libraries to be built as PIC (this is slower).
pulseaudio	Enable pulseaudio input support.
rtmp	Enable Real Time Messaging Protocol using librtmp instead the native implementation.
schroedinger	Enable Dirac video support (an advanced royalty-free video compression format) via libschroedinger (high-speed implementation in C of the Dirac codec).
ssl	Enable SSL/TLS support using dev-libs/openssl or net-libs/gnutls.
tools	Build and install small tools like aviocat, cws2fws, graph2dot, ismindex, qt-faststart.
twolame	Enable MP2 encoding via media-sound/twolame as an alternative to the internal encoder
vis	Adds support for SIMD optimizations for UltraSPARC processors.
vpx	Enable vp8 encoding support using media-libs/libvpx.
webp	Enable WebP encoding with media-libs/libwebp.
x265	Enable HEVC encoding with media-libs/x265.

libva-utils

drm	Enables VA/DRM API support.

makemkv

gui	Build the Qt5 GUI

minitube

download	Enable support for downloading YouTube videos

mjpegtools

sdlgfx	Enables y4mhist to display a graphical histogram

mjpg-streamer

input_control	Plugin giving ability to control camera movement (only specific cameras)
input_file	Plugin that watches given directory and send it's content
input_testpicture	Plugin for sending compiled in, test pictures
input_uvc	Plugin that sends video stream from UVC compatible camera
output_autofocus	Auto focusing plugin
output_file	Plugin that saves received content under given location
output_http	Small HTTP server plugin which sends WWW directory content and streams image content
output_rtsp	Plugin which provides a mechanism to take snapshots with a trigger from a UDP packet
output_udp	Plugin receiving content over UDP and storing to a directory
v4l	Uses media-libs/libv4l function mapping for input_uvc plugin
www	Installs WWW content

motion

mmal	Enables Multi-Media Abstraction Layer (MMAL) decoding support: Available e.g. on the Raspberry Pi.

motiontrack

multiprocess	Enables multi-process support (SMP/cluster) for motiontrack programs

mplayer

bl	Blinkenlights video output
bluray	Enable playback of Blu-ray filesystems
bs2b	Enable Bauer stereophonic-to-binaural headphone filter
cdio	Use libcdio for CD support (instead of cdparanoia)
cpudetection	Enables runtime CPU detection (useful for binpkgs, compatibility on other CPUs)
dvdnav	Use forked libdvdnav, navigate menus in GUIs
enca	Enables support for charset discovery and conversion
faac	Use external faac library for AAC encoding
faad	Use external faad library for AAC decoding
libmpeg2	Build support for mpeg2 over media-libs/libmpeg2 rather than using ffmpeg.
live	Enables live.com streaming media support
md5sum	Enables md5sum video output
mng	MNG input support
network	Enables network streaming support
nut	Enables support for the NUT container format
osdmenu	Enables support for on-screen display (OSD) menus
pnm	Add PNM video output option, to create PPM/PGM/PGMYUV images
pvr	Enable Video4Linux2 MPEG PVR
radio	Enable V4L2 radio interface and support
rar	Enable Unique RAR File Library
rtc	Enables usage of the linux real time clock. The alternative is software emulation of rtc
rtmp	Enables RTMPDump Streaming Media support
shm	Enable support for shm
tga	Enables Targa video output
toolame	Enable toolame MPEG-2 encoding
tremor	Enable internal support for Vorbis
twolame	Enable twolame MPEG-2 encoding
vcd	Enables VCD support
vidix	Support for vidix video output
xvmc	Enables X-Video Motion Compensation support
yuv4mpeg	Enables yuv4mpeg video output
zoran	Enables ZR360[56]7/ZR36060 video output

mpv

archive	Enable support for various archive formats via app-arch/libarchive
bluray	Enable playback of Blu-ray filesystems
cli	Build mpv CLI player
cplugins	Enable C plugins support
cuda	Enable hardware video decoding via Nvidia CUDA
drm	Enable Kernel Mode Setting / Direct Rendering Manager based video output
egl	Enable support for various EGL-based video outputs / backends
enca	Enable subtitles charset discovery via app-i18n/enca
gbm	Enable Graphics Buffer Manager based EGL video backend
jpeg	Enable support for saving screenshots in JPEG format
libass	Enable OSD (On Screen Display) and subtitles support via media-libs/libass
libguess	Enable subtitles charset discovery via app-i18n/libguess
libmpv	Build mpv shared library
lua	Enable Lua scripting, OSC (On Screen Controller) GUI and net-misc/youtube-dl hook-script
luajit	Use dev-lang/luajit instead of dev-lang/lua
opengl	Enable the recommended 'opengl' video output
raspberry-pi	Enable support for the Raspberry Pi
rubberband	Enable high quality pitch correction via media-libs/rubberband
sdl	Enable media-libs/libsdl2 based video and audio outputs (Note: these outputs exist for compatibility reasons only, avoid if possible)
tools	Install extra tools: mpv_identify.sh, mpv_idet.sh, and umpv
uchardet	Enable subtitles charset discovery via app-i18n/uchardet
vf-dlopen	Install additional video filters to be used with -vf dlopen

noad

libmpeg2	Support for libmpeg2 library

nvidia-settings

gtk3	Additionally build the GTK 3 library

nvidia_video_sdk

tools	Build and install example tools.

obs-studio

fdk	Enable libfdk support for AAC encoding.
imagemagick	Use ImageMagick for image loading instead of FFmpeg.

ogmrip

ogm	Support for OGM container format
srt	Support for SRT subtitle format

orion

mpv	Use the media-video/mpv player (upstream default) instead of the dev-qt/qtmultimedia one

parole

clutter	Compile in Clutter GTK+ support

qgifer

imagemagick	Use imagemagick for image operations
opencv3	Use media-libs/opencv:0/3.0 for video operations instead media-libs/opencv:0/2.4

rtmpdump

gnutls	Use GnuTLS library instead of the default OpenSSL

simplescreenrecorder

asm	Enable x86 assembly optimisation.
vpx	Enable VP8 codec support via media-libs/libvpx.

smplayer

autoshutdown	Enable the option to shutdown your computer after finishing the playlist. This requires dev-qt/qtdbus as dependency.
mpris	Enable support for MPRIS2 (Media Player Remote Interfacing Specification, version 2), a DBus interface for remote control, which requires dev-qt/qtdbus as dependency.

subtitlecomposer

mpv	Build mpv backend support

syncplay

client	Install Syncplay client
gui	Enable gui support
server	Install Syncplay server
vlc	Enable VLC2.x support

totem

lirc	Enable support for controlling Totem with a remote control using app-misc/lirc
nautilus	Enable the nautilus extension
python	Build support for dev-lang/python plugins
zeitgeist	Build the plugin to inject events to gnome-extra/zeitgeist

transcode

mjpeg	Enables mjpegtools support
nuv	NuppelVideo container format demuxing
pic	disable optimized assembly code that is not PIC friendly
postproc	Build with ffmpeg libpostproc support

tsmuxer

qt4	Installs tsMuxerGUI (needs Qt4)

vdr

alternatechannel	Use alternate channel on record
bidi	fribidi support, for languages, written from right to left
ddepgentry	remove duplicate EPG entries
dvlvidprefer	controls video-dir choice on recording
graphtft	support for media-plugins/vdr-graphtftplugin up from version 0.1.7
html	Install HTML documentation
jumpingseconds	skip seconds in played records
jumpplay	Enables automatic jumping over cut marks while watching a recording
kbd	enable keyboard support as remote device
mainmenuhooks	Allows to replace main menu entries by some special plugins (like epgsearch, extrecmenu, ...)
menuorg	Enables support for the media-plugins/vdr-menuorg
menuselection	adds support for menu hotkeys of double digits
naludump	Removes NALU fill data from h.264-Streams of TS files
permashift	permanent timeshift by recording live TV on hard disk, need plugin media-plugins/vdr-permashift
permashift_v1	permanent timeshift by recording live TV on RAM, need plugin >=mediaplugins/vdr-permashift-1
pinplugin	Support for media-plugins/vdr-pin
resumereset	rreset resume of EOF
rotor	Enable support for plugin media-plugins/vdr-rotor for dish-positioner.
ttxtsubs	support for media-plugins/vdr-ttxtsubs
vasarajanauloja	replacement for the liemikuutio patch, adds some nice must haves features
wareagleicon	Replace original icon set in menu
yaepg	Enables support for the vdr-yaepg plugin

vlc

X	Enables support for, e.g., fullscreen mode via the X Window System. By itself, this flag does not build a graphical interface.
aom	Enables experimental support for AV1 codec
archive	Enables support for libarchive stream extractor
atmo	Enables support for AtmoLight (homebrew Ambient Lighting Technology)
audioqueue	Enables AudioQueue audio module for Mac OS X.
avcodec	Enables libavcodec support for video/audio encoding/decoding. libavcodec is part of FFmpeg.
avformat	Enables libformat support for reading and writing various media containers. libavformat is part of FFmpeg.
bluray	Enables libbluray for Blu-ray disc support.
chromaprint	Enables libchromaprint for Chromaprint based audio fingerprinter support.
chromecast	Enable experimental support for Google Chromecast.
dc1394	Enables IIDC cameras support.
directx	Enable Win32 DirectX support.
dvbpsi	Enables support for Mpeg-TS files (.ts, .m2ts, .mts) via media-libs/libdvbpsi.
dxva2	Enables Win32 DxVA2 support.
faad	Enable AAC audio decoding library support via media-libs/faad2.
fdk	Enables the Fraunhofer AAC codec library.
fluidsynth	Enables Fluidsynth MIDI software synthesis (with external sound fonts).
gcrypt	Enables cryptography support via libgcrypt.
gme	Enables support for media-libs/game-music-emu for playing various video game music formats.
gnome	Adds support for GNOME's filesystem abstraction layer, gnome-base/gnome-vfs. This flag is not GUI-related.
growl	Enables growl notification support (over UDP for remote access and native on OSX)
gstreamer	Enables GStreamer based decoding support (currently supports only video decoding)
httpd	Enables a web based interface for vlc.
kate	Adds support for Ogg Kate subtitles via libkate.
libtar	Uses libtar instead of the built-in tar reader for reading custom skins.
libtiger	Enables Ogg Kate subtitles rendering using libtiger.
linsys	Enables support for Linux Linear Systems Ltd. SDI and HD-SDI input cards.
live	Enables live555 streaming media support (client support for rtsp).
lua	Enable Lua scripting support, needed for including support for Jamendo (online music platform) and similar things.
macosx-dialog-provider	Enables Mac OS X dialog module.
macosx-eyetv	Enables Mac OS X EyeTV (TNT Tuner) module.
macosx-notifications	Enables Mac OS X notifications module (formerly growl).
macosx-qtkit	Enables Mac OS X qtkit module: qtcapture (video) and qtsound (audio) module.
macosx-quartztext	Enables Mac OS X quartz text module.
matroska	Enables matroska support using reference libraries (fallback on other existing matroska support if disabled, i.e., matroska enabled FFmpeg)
mpeg	Add libmpeg2 support for mpeg-1 and mpeg-2 video streams
nfs	Enables support for nfs protocol via net-fs/libnfs
omxil	Enables OpenMAX Integration Layer codec module.
opencv	Enabled OpenCV (computer vision) filter module.
optimisememory	Enable optimisation for memory rather than performance.
opus	Support opus decoding via libopus.
postproc	Enables image post-processing via libpostproc (part of FFmpeg).
projectm	Enables the projectM visualization plugin.
qt4	Builds a Qt4 based frontend, a graphical interface.
qt5	Builds a Qt5 based frontend, a graphical interface (overrides qt4).
rtsp	Enables real audio and RTSP modules.
run-as-root	Allows vlc to start for root. Don't enable this unless you have a very specific (e.g. embedded) need for it!
schroedinger	Enable Dirac video support (an advanced royalty-free video compression format) via libschroedinger (high-speed implementation in C of the Dirac codec).
sdl-image	Enables sdl image video decoder (depends on sdl)
sftp	Enables libssh2 to support SFTP file transfer.
shout	Enables libshout output.
sid	Adds support for playing C64 SID files through media-libs/libsidplay:2.
skins	Enables support for the skins2 interface.
swscale	Enables image scaling and conversion via libswscale (part of FFmpeg).
tremor	Enables tremor, a fixed-point version of the Ogg Vorbis decoder.
twolame	Enables twolame support (MPEG Audio Layer 2 encoder).
upnp	Enables support for the Intel SDK stack based UPnP discovery module instead of CyberLink.
vcdx	Enables VCD with navigation via libvcdinfo (depends on cdio)
vlm	New videolan (media) manager (vlm), a little manager designed to launch and manage multiple streams from within one instance of VLC.
vpx	Enables the decoder(s) from the WebM VP8 / VP9 Codec SDK.
wma-fixed	Enables fixed point WMA decoder.
x265	Support X265 Encoder.
xcb	Support the X C-language Binding, a replacement for Xlib; !!! you will need this option to be able to integrate video in the Qt interface, see bug #500678.
zeroconf	Enables support for zero-configuration networking via avahi.
zvbi	Enables support for teletext subtitles via the zvbi library.

webcamoid

headers	Install development headers
libuvc	Build with libuvc support
qtaudio	Enable audio capture/play via dev-qt/qtmultimedia
v4lutils	Build with V4L-utils support
videoeffects	Build video effects

x264-encoder

10bit	Set output bit depth to 10
avs	enable AvxSynth support in the AviSynth input module
ffmpegsource	Enable ffmpegsource aka ffms support, disables lavf
interlaced	Enable interlaced encoding support, this can decrease encoding speed by up to 2%

xine-ui

vdr	Enables Video Disk Recorder support

net-analyzer

2ping

server	Install the server init scripts.

argus

libtirpc	Build against net-libs/libtirpc for RPC support

argus-clients

ft	Enable support for flow packets through net-analyzer/flow-tools

barnyard

sguil	Enable sguil (The Analyst Console for Network Security Monitoring) support

barnyard2

gre	Enable GRE support
mpls	Enable support for mpls networks

bro

broccoli	Enable the Bro Client Communication Library
broctl	An interactive shell for managing Bro installations
broker	Bro's new Messaging Library (experimental)
geoip	Enable support for Maxmind's GeoIP library
ipv6	Support for mobile IPv6
jemalloc	Support for the Jemalloc allocator
python	Enable Python bindings
ruby	Enable Ruby bindings (deprecated)
tcmalloc	Enable Google's Performance Analysis Tools
tools	Small auxiliary tools for Bro

bwm-ng

csv	Enable csv output
html	Enable html output

cacti

doc	install html documentation

check_mk

agent-only	Install only the check_mk agent.
apache_status	Install check_mk-agent apache-status plugin.
dmi_sysinfo	Install check_mk-agent dmi_sysinfo plugin.
livestatus	Enable livestatus.
logwatch	Install check_mk-agent logwatch plugin.
mysql	Install check_mk-agent mysql plugin.
nagios4	Depend on net-analyzer/nagios-core-4
nfsexports	Install check_mk-agent nfsexports plugin.
postgres	Install check_mk-agent postgres plugin.
smart	Install check_mk-agent S.M.A.R.T plugin.
wato	Enable check_mk WATO - check_mk's Web Administration Tool.
zypper	Install check_mk-agent zypper plugin.

check_mk_agent

apache_status	Install check_mk-agent apache-status plugin.
logwatch	Install check_mk-agent logwatch plugin.
mysql	Install check_mk-agent mysql plugin.
nfsexports	Install check_mk-agent nfsexports plugin.
postgres	Install check_mk-agent postgres plugin.
smart	Install check_mk-agent S.M.A.R.T plugin.
zypper	Install check_mk-agent zypper plugin.

echoping

http	enable support for http protocol.
icp	enable support for ICP (used to monitor proxies).
priority	enable socket priority support.
smtp	enable support for SMTP protocol.
tos	enable support for TOS (TYpe Of Service).

ettercap

plugins	Install ettercap plugins (et_*.so)

flent

plots	Enable drawing plots

flowgrind

pcap	Enable packet capturing support using net-libs/libpcap

fprobe

messages	enable console messages

goaccess

btree	Enable Tokyo Cabinet's on-disk B+ Tree database backend
geoipv2	Enable support for GeoIP2 through dev-libs/libmaxminddb
getline	Use GNU getline() to parse full line requests
memhash	Enable Tokyo Cabinet's on-memory hash database backend
tokyocabinet	Enable Tokyo Cabinet's on-memory hash database backend

gr-fosphor

glfw	enable GLFW based interface

graphite-web

carbon	Enable carbon support
memcached	Enable memcached support

hexinject

experimental	Install experimental packets.tcl
tools	Install hex2raw and prettypacket tools

httping

tfo	Enable support for TCP Fast Open

hydra

ncp	NCP protocol (NetWare) support through net-fs/ncpfs

icinga

contrib	additional scripts
eventhandler	Adds support for running custom scripts whenever a host or service state change occurs
idoutils	Adds DB support
lighttpd	Adds Lighttpd support
plugins	Adds support for nagios plugins
web	Adds generic web interface support

icinga-web

pnp	Enables pnp4nagios integration

icinga2

classicui	Adds support for the old interface
console	Adds support for line-editing in the console
lto	Adds support for link time optimization
mail	Allows for mailing of alerts
nano-syntax	Adds support for syntax used in the nano editor
plugins	Adds support for nagios plugins
studio	Adds support for Icinga-studio

ipsumdump

nanotimestamp	Enable timestamps with nano-second resolution

linkchecker

sqlite	Mozilla Bookmark parsing

mate-netspeed

gtk3	Build with GTK+3 instead of GTK+2

metasploit

development	Install dependencies needed for metasploit and exploit development
nexpose	Enable the plugin to integrate with nexpose
openvas	Enable the plugin to integrate net-analyzer/openvas
oracle	Enable restricted oracle modules which have additional deps
pcap	Enable libpcap for packet sniffing

mk-livestatus

nagios4	Generate a net-analyzer/nagios-4 compatible plugin

monitoring-plugins

dns	Install net-dns/bind-tools required for monitoring DNS servers. Disabling the flag does not remove any plugins.
fping	Install net-analyzer/fping required for fancy ping monitoring. Disabling the flag does not remove any plugins.
game	Install games-util/qstat required for monitoring FPS servers. Disabling the flag does not remove any plugins.
snmp	Install dev-perl/Net-SNMP and net-analyzer/net-snmp required for monitoring SNMP values. Disabling the flag does not remove any plugins.
ssh	Install net-misc/openssh required for monitoring SSH servers. Disabling the flag does not remove any plugins.

munin

apache	Set up the configuration of the CGI generation of HTML and graphs to work with Apache. This also install an include-able configuration file.
asterisk	Install the packages required for monitoring Asterisk. Disabling the flag does not remove any plugin files.
cgi	Install the CGI-compatible scripts for on-the-fly generation of web pages and graphs. This is only meaningful if the minimal USE flag is disabled.
dhcpd	Install dev-perl/Net-IP, dev-perl/HTTP-Date and net-misc/dhcp to monitor DHCP lease usage. This only works if the server is on the same system as the node, so the server is also brought in. Disabling the flag does not remove any plugin file.
doc	Build and install a local copy of the HTML documentation for the whole software. This requires dev-python/sphinx to process the documentation sources.
http	Install dev-perl/libwww-perl required for monitoring HTTP-based services such as Apache and nginx. Disabling the flag does not remove any plugin file.
ipmi	Install sys-apps/ipmitool required for monitoring IPMI sensors. Disabling the flag does not remove any plugin file.
ipv6	Add support for IPv6 in munin-node. IPv6 support for the master is always enabled, but the node requires a newer version of dev-perl/Net-Server, capable of listening to IPv6 sockets.
irc	Install the packages required for monitoring IRC. Disabling the flag does not remove any plugin files.
java	Build the Java-based plugins to monitor JMX-compatible applications. Disabling the flag removes the jmx monitoring plugins.
memcached	Install the packages required for memcached monitoring. Disabling the flag does not remove any plugin files.
minimal	Only install munin-node and its plugins. This excludes the scripts to generate the web pages and the graphs.
mysql	Install the packages required for monitoring MySQL. Disabling the flag does not remove any plugin files.
postgres	Install the packages required for monitoring PostgreSQL. Disabling the flag does not remove any plugin files.
syslog	Configure the node by default to log on syslog. This requires the presence of virtual/perl-Sys-Syslog. As of version 2.0.2, the master scripts only log to file, and not to syslog.

nagios-core

classicui	use the classic web theme
lighttpd	install www-servers/lighttpd config
web	enable web interface

nagios-plugin-check_raid

3ware	Support 3ware RAID controllers
aacraid	Support Adaptec AAC-RAID controllers
dmraid	Support Device-Mapper RAID
hpa	Support HP Array controllers
hpsa	Support HP SmartArray (CCISS) controllers
i2o	Support DPT-I2O controllers (mostly Adaptec)
megaraid-sas	Support LSI MegaRAID SAS controllers
megaraid-scsi	Support LSI MegaRAID SCSI controllers
mpt	Support LSI MPT Fusion controllers
mpt-sas2	Support LSI SAS-2 controllers

nagios-plugins

nagios-dns	Install net-dns/bind-tools required for monitoring DNS servers. Disabling the flag does not remove any plugin file.
nagios-game	Install games-util/qstat required for monitoring FPS servers. Disabling the flag does not remove any plugin file.
nagios-ping	Install net-analyzer/fping required for fancy ping monitoring. Disabling the flag does not remove any plugin file.
snmp	Install dev-perl/Net-SNMP required for monitoring SNMP values. Disabling the flag does not remove any plugin file.
ssh	Install net-misc/openssh required for monitoring SSH servers. Disabling the flag does not remove any plugin file.

nagios-plugins-flameeyes

smart	Install sys-apps/smartmontools required for S.M.A.R.T. disk monitoring. Disabling the flag removes the plugin file. This plugin also requires the sudo flag to be enable.

nagvis

automap	Enable automated map generation using media-gfx/graphviz

net-snmp

elf	Enable the use of elf utils to check uptime on some systems
mfd-rewrites	Use MFD rewrites of mib modules where available
netlink	Use dev-libs/libnl to fetch TCP statistics instead of using /proc/net/tcp (Linux only).
pci	Use libpci (from sys-apps/pciutils) to look up network interface description. This feature is only available on Linux.
rpm	Enable monitoring of app-arch/rpm. This flag requires the bzip2 and zlib flags to be enabled as well.
smux	Enable support for the legacy smux protocol (superseded by agentx)
ucd-compat	Build UCD compatibility library. Increases significantly the install size.

netdata

compression	Enable compression via zlib
ipmi	Install sys-apps/ipmitool required for monitoring IPMI sensors.
nfacct	Enable the nfacct plugin
nodejs	Enable use of nodejs (which some plugins use)

netperf

demo	Emit interim results during the run. May affect results

nfdump

compat15	Enable read support for nfdump data files created with nfdump 1.5.x
ftconv	Build the flow-tools to nfdump converter
nfprofile	Build nfprofile used by NfSen
nftrack	Build nfprofile used by PortTracker
readpcap	Build nfcapd collector to read from pcap file instead ofnetwork data
sflow	Build sflow collector sfcpad

nmap

libssh2	Enable SSH support through net-libs/libssh2
ncat	Install the ncat utility
ndiff	Install the ndiff utility
nmap-update	Install nmap-update, which uses dev-vcs/subversion to update nmap scripts in your home directory
nping	Install the nping utility
nse	Include support for the Nmap Scripting Engine (NSE)
system-lua	Use dev-lang/lua instead of the bundled liblua
zenmap	Install the GTK+ based nmap GUI, zenmap

nrpe

command-args	Build support for specifying the command-line arguments from the Nagios/Icinga master. Make sure you understand the implications of this flag as it can be a security risk.
minimal	Only build the check plugins for Nagios/Icinga, and not the daemon.

nsca

crypt	Build support for crypted communication with nsca, through dev-libs/libmcrypt. It's recommended not to disable this flag unless all the communication will be handled in an absolutely safe environment.
minimal	Only build and install the send_nsca command and not the daemon. This allows a very minimal install with no overhead when setting up a node.

openvas

pdf	Enable pdf report creation

pchar

pcap	Use the net-libs/libpcap library

pinger

gtk2	Install the gtkpinger GUI utility based on x11-libs/gtk+:2
gtk3	Install the gtkpinger GUI utility based on x11-libs/gtk+:3

pmacct

64bit	Use 64bit counters instead of 32bit ones
geoipv2	Enable support for GeoIP2 through dev-libs/libmaxminddb
jansson	Enable support for JSON through dev-libs/jansson
kafka	Enable support for Apache Kafka through dev-libs/librdkafka
mongodb	Enable support for MongoDB through dev-libs/mongo-c-driver
ndpi	Enable support for nDPI through net-libs/nDPI
nflog	Enable support for NFLOG through uacctd
rabbitmq	Enable support for RabbitMQ through net-libs/rabbitmq-c
ulog	Enable support for ULOG in older kernels (deprecated)
zmq	Enable support for ZeroMQ through net-libs/zeromq

pnp4nagios

icinga	Build against net-analyzer/icinga2 or net-analyzer/icinga instead of net-analyzer/nagios-core
nagios	Build against net-analyzer/nagios-core (the default)

prelude-lml

tls	Enables Prelude LML support Syslog through TLS using net-libs/gnutls.

rrdcollect

exec	Enable exec:/// support
librrd	Use the librrd library from net-analyzer/rrdtool

rrdtool

graph	Enable support for graphing functions
rados	Enable support for librados from sys-cluster/ceph
rrdcgi	Build rrdcgi support

sancp

sguil	Enable sguil (The Analyst Console for Network Security Monitoring) support

sarg

gd	Enable support for graphs in reports through media-libs/gd
pcre	Enable support for regular expressions in the hostalias file through dev-libs/libpcre

scanlogd

nids	Use net-libs/libnids for packet capturing
pcap	Use net-libs/libpcap for packet capturing

scapy

pyx	Enable dev-python/pyx support for psdump/pdfdump commands
tcpreplay	Enable net-analyzer/tcpreplay support for fast packet replay
visual	Enable dev-python/visual support for 3d graphs

smokeping

dig	Install net-dns/bind-tools for dig functionality
echoping	Install net-analyzer/echoping for echoping functionality
ssh	Install ssh functionality
telnet	Install dev-perl/Net-Telnet for telnet functionality

snort

active-response	Enables support for automatically sending TCP resets and ICMP unreachable messages to terminate connections. Used with inline deployments.
control-socket	Enables Snort's control socket.
dynamicplugin	Enable ability to dynamically load preprocessors, detection engine, and rules library. This is required if you want to use shared object (SO) snort rules.
file-inspect	Enables extended file inspection capabilities.
flexresp3	Enables support for new flexable response preprocessor for enabling connection tearing for inline deployments. Replaces flexresp and flexresp2.
gre	Enable support for inspecting and processing Generic Routing Encapsulation (GRE) packet headders. Only needed if you are monitoring GRE tunnels.
high-availability	Enables high-availability state sharing.
inline-init-failopen	Enables support to allow traffic to pass (fail-open) through inline deployments while snort is starting and not ready to begin inspecting traffic. If this option is not enabled, network traffic will not pass (fail-closed) until snort has fully started and is ready to perform packet inspection.
large-pcap-64bit	Allows Snort to read pcap files that are larger than 2 GB. ONLY VALID FOR 64bit SYSTEMS!
libtirpc	Build against net-libs/libtirpc for RPC support
linux-smp-stats	Enable accurate statistics reporting through /proc on systems with multipule processors.
mpls	Enables support for processing and inspecting Multiprotocol Label Switching MPLS network network traffic. Only needed if you are monitoring an MPLS network.
non-ether-decoders	Enable decoding of non-ethernet protocols such as TokenRing, FDDI, IPX, etc.
normalizer	Enables support for normalizing packets in inline deployments to help minimize the chances of detection evasion.
paf	Enables support for Protocol Aware Flushing. This allows Snort to statefully scan a stream and reassemble a complete protocol data unit regardless of segmentation.
perfprofiling	Enables support for preprocessor and rule performance profiling using the perfmonitor preprocessor.
ppm	Enables support for setting per rule or per packet latency limits. Helps protect against introducing network latency with inline deployments.
react	Enables support for the react rule keyword. Supports interception, termination, and redirection of HTTP connections.
reload-error-restart	Enables support for completely restarting snort if an error is detected durring a reload.
shared-rep	Enables the use of shared memory for the Reputation Preprocessor (Only available on Linux systems)
side-channel	Enables Snort's the side channel.
sourcefire	Enables Sourcefire specific build options, which include --enable-perfprofiling and --enable-ppm.
targetbased	Enables support in snort for using a host attibute XML file (attribute_table.dtd). This file needs to be created by the user and should define the IP address, operating system, and services for all hosts on the monitored network. This is cumbersome, but can improve intrusion detection accuracy.
zlib	Enables HTTP inspection of compressed web traffic. Requires dynamicplugin be enabled.

suricata

af-packet	Enable AF_PACKET support
control-socket	Enable unix socket
cuda	Enable NVIDIA Cuda computations support
detection	Enable detection modules
logrotate	Install logrotate rule
luajit	Enable Luajit support
nflog	Enable libnetfilter_log support
nfqueue	Enable NFQUEUE support for inline IDP
redis	Enable Redis support
rules	Install default ruleset

symon

perl	Enables a generic perl symux client
symon	Enables the system monitor. Offers no functionality but monitoring and forwarding of measured data
symux	Enables the multiplexer which stores incoming symon streams on disk in RRD (net-analyzer/rrdtool) files

tcpdump

drop-root	Drop privileges to tcpdump:tcpdump when run as root
smi	Build with net-libs/libsmi to load MIBs on the fly to decode SNMP packets

tcpreplay

pcapnav	Enable if you want the jump to byte offset feature via net-libs/libpcapnav
tcpdump	Use net-analyzer/tcpdump for packet decoding feature

testssl

bundled-openssl	Install precompiled versions of OpenSSL for greater testing coverage

wireshark

adns	Use the GNU net-dns/c-ares library to resolve DNS names
androiddump	Install androiddump, an extcap interface to capture from Android devices
capinfos	Install capinfos, to print information about capture files
captype	Install captype, to print the file types of capture files
ciscodump	Install ciscodump, extcap interface to capture from a remote Cisco router
crypt	Use dev-libs/libgcrypt to decrypt traffic
dftest	Install dftest, to display filter byte-code, for debugging dfilter routines
doc-pdf	Build documentation in pdf format (US and a4 paper sizes)
dumpcap	Install dumpcap, to dump network traffic from inside wireshark
editcap	Install editcap, to edit and/or translate the format of capture files
libssh	Use net-libs/libssh (for sshdump)
libxml2	Use dev-libs/libxml2 for handling XML configuration in dissectors
lz4	Use app-arch/lz4 for compression/decompression
mergecap	Install mergecap, to merge two or more capture files into one
netlink	Use dev-libs/libnl
nghttp2	Use net-libs/nghttp2 for HTTP/2 support
pcap	Use net-libs/libpcap for network packet capturing (build dumpcap, rawshark)
randpkt	Install randpkt, a utility for creating pcap trace files full of random packets
randpktdump	Install randpktdump, an extcap interface to provide access to the random packet generator (randpkt)
reordercap	Install reordercap, to reorder input file by timestamp into output file
sbc	Use media-libs/sbc for playing back SBC encoded packets
sharkd	Install sharkd, the daemon variant of wireshark
smi	Use net-libs/libsmi to resolve numeric OIDs into human readable format
snappy	Use app-arch/snappy for snappy compression and decompression
spandsp	Use media-libs/spandsp for for G.722 and G.726 codec support in the RTP Player
sshdump	Install sshdump, an extcap interface to capture from a remote host through SSH
text2pcap	Install text2pcap, to generate a capture file from an ASCII hexdump of packets
tfshark	Install tfshark, a terminal-based version of the FileShark capability
tshark	Install tshark, to dump and analyzer network traffic from the command line
udpdump	Install udpdump, to get packets exported from a source (like a network device or a GSMTAP producer) that are dumped to a pcap file

zabbix

agent	Enable zabbix agent (for to-be-monitored machines)
frontend	Enable zabbix web frontend
ipv6	Turn on support of IPv6
java	Enable Zabbix Java JMX Management Gateway
libxml2	Use libxml2 client library
odbc	Enable Database Monitor and use UnixODBC Library by default
openipmi	Enable openipmi things
proxy	Enable proxy support
server	Enable zabbix server
ssh	SSH v2 based checks
static	Build statically linked binaries

zmap

json	Add support to store results JSON based
mongo	Add support for storing in a mongo DB via dev-db/mongodb
redis	Add support for storing in a redis DB via dev-libs/hiredis

net-dialup

accel-ppp

ipoe	Build IPoE kernel module
shaper	Support for traffic shaping
valgrind	Compile in valgrind hints

freeradius

pcap	Build the RADIUS sniffer which requires net-libs/libpcap.

freeradius-client

scp	Add service type hints derived from username prefix
shadow	Enable shadow password support

mgetty

fax	Enables fax support
fidonet	Enables FidoNet support

ppp

activefilter	Enables active filter support
atm	Enables ATM (Asynchronous Transfer Mode) protocol support
dhcp	Installs PPP DHCP client plugin for IP address allocation by a DHCP server (see http://www.netservers.co.uk/gpl/)
eap-tls	Enables support for Extensible Authentication Protocol and Transport Level Security (see http://www.nikhef.nl/~janjust/ppp/index.html)
gtk	Installs GTK+ password prompting program that can be used by passprompt.so PPP plugin for reading the password from a X11 input terminal
ipv6	Enables support for IP version 6
pam	Enables PAM (Pluggable Authentication Modules) support
radius	Enables RADIUS support

xl2tpd

dnsretry	Patch for host lookup retries, activated by redial feature
kernel	Enable kernel interface for PPPoL2TP

net-dns

avahi

autoipd	Build and install the IPv4LL (RFC3927) network address configuration daemon
bookmarks	Install the avahi-bookmarks application (requires dev-python/twisted-core and dev-python/twisted-web)
gtk3	Build the avahi-ui-gtk3 library, and use gtk3 for the avahi utilities under USE=utils
howl-compat	Enable compat libraries for howl
mdnsresponder-compat	Enable compat libraries for mDNSResponder
utils	Install the avahi gtk+ utils avahi-discover, bssh, and bvnc

bind

dlz	Enables dynamic loaded zones, 3rd party extension
dnstap	Enables dnstap packet logging
filter-aaaa	Enable filtering of AAAA records over IPv4
fixed-rrset	Enables fixed rrset-order option
gost	Enables gost OpenSSL engine support
gssapi	Enable gssapi support
json	Enable JSON statistics channel
lmdb	Enable LMDB support to store configuration for 'addzone' zones
nslint	Build and install the nslint util
rpz	Enable response policy rewriting (rpz)
urandom	Use /dev/urandom instead of /dev/random

bind-tools

gost	Enables gost OpenSSL engine support
gssapi	Enable gssapi support
urandom	Use /dev/urandom instead of /dev/random

ddclient

cloudflare	Enable support for updating IP address via CloudFlare
hardened	Use iproute2 instead of ifconfig to grab an IP address

dnscrypt-proxy

plugins	Enable plugin support to inspect and modify queries and responses
systemd	Use systemd's socket activation instead of creating the sockets itself

dnsdist

dnscrypt	Enable the ability to act as a DNSCrypt server
luajit	Use dev-lang/luajit instead of dev-lang/lua
regex	Enable support for regular expression matching via dev-libs/re2
remote-logging	Enable support for remote logging via dev-libs/protobuf
ssl	Enable support for and encrypted client-server communication via dev-libs/libsodium

dnsmasq

auth-dns	Add support for acting as an authorative DNS server.
conntrack	Add support for Linux conntrack connection marking.
dhcp	Enable support for acting as a DHCP server.
dhcp-tools	Install extra command line tools for manually managing DHCP leases.
dnssec	Enable support DNSSEC validation and caching.
id	Whether report *.bind CHAOS info to clients, otherwise forward such requests upstream instead
libidn2	Enable support for Internationalized Domain Names, via net-dns/libidn2 rather than net-dns/libidn
script	Enable support for calling scripts when leases change.
tftp	Enables built in TFTP server for netbooting.

dnssec-validator

ecdsa-check	Requires openssl[-bindist]

hash-slinger

ipsec	Enable support for IPSECKEY records (ipseckey)
openpgp	Enable support for OPENPGPKEY records (openpgpkey)
ssh	Enable support for SSHFP records (sshfp)

knot

dnsproxy	Enable the tiny DNS proxy module
dnstap	Include support for the dnstap binary log format (http://dnstap.info/)
fastparser	Use a zone file parser that is faster, but requires more memory and CPU time to compile
libidn2	If IDN support is enabled, use net-dns/libidn2 instead of net-dns/libidn
noudp	Enable the module which can send empty truncated responses to UDP queries
onlinesign	Enable the module that sign zones on the fly instead of pre-signing zone
rosedb	Enable the module that staticaly override certain responses
rrl	Enable the response rate limiting module
stats	Enable the server statistics module
synthrecord	Enable the automatic forward/reverse records module
utils	Install Knot utilities, such as kdig, kzonecheck, ...
whoami	Enable the whoami response module

ldns-utils

dane	Enable DNS-based Authentication of Named Entities (DANE) support
ecdsa	Enable ECDSA support
gost	Enable GOST support

maradns

authonly	Allows one to build only authoritative DNS server

mydns

alias	Enable David Phillips aliasing
status	Enable the STATUS opcode to check server status

nsd

bind8-stats	Enables BIND8 like NSTATS and XSTATS
libevent	Use libevent or libev, useful when zone count is high
minimal-responses	If minimal responses are disabled, responses are more likely to get truncated, resulting in TCP fallback
munin	Install a plugin for net-analyzer/munin to graph statistical data from nsd.
nsec3	Enable NSEC3 support
ratelimit	Enables ratelimiting, based on query name, type and source
root-server	Configure NSD as a root server
runtime-checks	Enable runtime checks, this could lead to a reduced service level

opendnssec

auditor	Enables auditing capabilities for OpenDNSSEC
eppclient	Enables support for automatic submission of DNSSEC keys to an upstream epp server
external-hsm	Enables support for storing DNSSEC keys through an arbitrary non-portage PKCS#11 interface, specified through an environment variable
opensc	Enables support for storing DNSSEC keys through a dev-libs/opensc PKCS#11 interface
signer	Enables signing capabilities for OpenDNSSEC
softhsm	Enables support for storing DNSSEC keys in a dev-libs/softhsm PKCS#11 object

pdns

botan	Make it possible to use the dev-libs/botan library for crypto-related stuff (like DNSSec) which can be significantly faster than PolarSSL.
luajit	Enable support for dev-lang/luajit
mydns	Making it possible to use a MyDNS MySQL database with PowerDNS (not recommended for new deployments).
opendbx	Use a database supported by dev-db/opendbx as backend.
protobuf	Enable support for dev-libs/protobuf.
remote	Use a generic socket or pipe as a backend (via JSON RPC requests).
sodium	Use dev-libs/libsodium for cryptography
tinydns	Use a TinyDNS CDB database as backend.
tools	Build optional tools (dnsscan, dnsscope, etc..).

pdns-recursor

luajit	Enable support for dev-lang/luajit.
protobuf	Enable support for dev-libs/protobuf.
sodium	Use dev-libs/libsodium for cryptography

pdnsd

isdn	Linux-only: check status of ippp interfaces with ISDN-specific system calls.
urandom	Linux-only: use /dev/urandom (pseudo-random number generation) instead of the default use of random() PRNG.

resolvconf-symlink

symlink	Actually replace /etc/resolv.conf with a symlink. Without this flag, the ebuild is a no-op.

unbound

dnscrypt	Enable DNSCrypt support
dnstap	Enable dnstap support
ecdsa	Enable ECDSA support
gost	Enable GOST support

net-firewall

arno-iptables-firewall

plugins	Install optional plugins

conntrack-tools

libtirpc	Build against net-libs/libtirpc for RPC support

ebtables

perl	Install the ebtables-save script which uses perl

firehol

ipset	Use net-firewall/ipset.

firewalld

gui	Builds and installs GUI configurator and GTK+ applet

fwknop

client	Build fwknop client
extras	Install utility scripts and AppArmor policy for fwknopd
firewalld	Use net-firewall/firewalld as the default server backend
gdbm	Use sys-libs/gdbm to store fwknopd digest cache
gpg	Enable GPG support via app-crypt/gpgme
iptables	Use net-firewall/iptables as the default server backend
nfqueue	Enable UDP-only NFQUEUE server mode (no net-libs/libpcap dependency)
server	Build fwknopd server
udp-server	Enable UDP-only server mode (no net-libs/libpcap dependency)

ipt_netflow

natevents	Netflow NAT translation events (NEL) support

iptables

conntrack	Build against net-libs/libnetfilter_conntrack when enables the connlabel matcher
netlink	Build against libnfnetlink which enables the nfnl_osf util
nftables	Support nftables kernel interface
pcap	Build against net-libs/libpcap which enables the nfbpf_compile util

nufw

nfconntrack	Use netfilter_conntrack
nfqueue	Use NFQUEUE instead of QUEUE
pam_nuauth	Add support for pam nufw from PAM
plaintext	Add support for authentication with plaintext files

pftop

altq	Enable altq(4) support — alternate queuing of network packets.

pglinux

cron	Install cron script
logrotate	Install logrotate.d file

shorewall

init	Adds the capability to place the firewall in a safe state prior to bringing up the network interfaces
ipv4	Installs everything needed to create a full IPv4 firewall
ipv6	Adds the capability to create a full IPv6 firewall (requires net-firewall/shorewall ipv4 USE flag)
lite4	Installs everything needed to just *run* an IPv4 compiled firewall script created with net-firewall/shorewall ipv4 USE flag
lite6	Installs everything needed to just *run* an IPv6 compiled firewall script created with net-firewall/shorewall ipv6 USE flag

ufw-frontends

kde	Use kdesu to gain root privileges (note: the flag has lower priority than "policykit")
policykit	Use pkexec to gain root privileges

net-fs

autofs

dmalloc	Enable debugging with the dmalloc library
hesiod	Install hesiod module
ldap	Install LDAP module
libtirpc	Use TiRPC library instead of SunRPC
mount-locking	Enable locking to prevent corruption of /etc/mtab in the presence of concurrent auto-mounting. If enabled, recursive auto-mounting (eg. using autofs to bind or loop mount a filesystem which is itself auto-mounted) is not possible.
sasl	Enable SASL support in the LDAP module

cifs-utils

ads	Enable Active Directory support and create cifs.idmap binary - idmap support
caps	libcap support
caps-ng	libcap-ng support
creds	cifs credentials support

cvmfs

aufs	Use AUFS instead of OverlayFS for the server
preload	Install the cvmfs cache preloader for distributed file systems
server	Install the cvmfsd program and init script
test-programs	Install unit test programs

netatalk

pgp	Add support pgp authentication module
quota	Add support for user quota on various filesystems
shadow	Add shadow support
ssl	Use dev-libs/openssl to provide DHX User Access Modules. These are not used with most recent versions of OS X and can be kept disabled without risks.
tracker	Add support for spotlight like tracker
utils	Install afpstats script

nfs-utils

ldap	Add ldap support
libmount	Link mount.nfs with libmount
nfsdcld	Enable nfsdcld NFSv4 clientid tracking daemon
nfsidmap	Enable support for newer nfsidmap helper
nfsv4	Enable support for NFSv4
nfsv41	Enable support for NFSv4.1
uuid	Support UUID lookups in rpc.mountd

openafs

bitmap-later	Enable fast startup of file server by not reading bitmap till needed.
fuse	Build fuse client.
modules	Build libafs kernel module. Disable only if you know what you're doing: without this module OpenAFS client will not work.
pthreaded-ubik	Enable installation of pthreaded ubik applications.
supergroups	Enable support for nested pts groups.

s3fs

gnutls	Enable net-libs/gnutls crypto backend
nettle	Use dev-libs/nettle network functions with GnuTLS.
nss	Enable dev-libs/nss crypto backend
openssl	Enable dev-libs/openssl crypto backend

s3ql

contrib	Install additional contributed scripts

samba

addc	Enable Active Directory Domain Controller support
addns	Enable AD DNS integration
ads	Enable Active Directory support
aio	Enable asynchronous IO support
ceph	Enable support for Ceph distributed filesystem via sys-cluster/ceph
client	Enables the client part
cluster	Enable support for clustering
dmapi	Enable support for DMAPI. This currently works only in combination with XFS.
gpg	Use app-crypt/gpgme for AD DC
iprint	Enabling iPrint technology by Novell
quota	Enables support for user quotas
system-heimdal	Use app-crypt/heimdal instead of bundled heimdal.
system-mitkrb5	Use app-crypt/mit-krb5 instead of app-crypt/heimdal.
winbind	Enables support for the winbind auth daemon

smbnetfs

gnome	Use the gnome-base/gnome-keyring for password management.

net-ftp

frox

transparent	Enable transparent proxying of data connections

lftp

convert-mozilla-cookies	Install the convert-mozilla-cookies script and its run-time dependencies
verify-file	Install the verify-file script and its run-time dependencies

proftpd

authfile	Enable support for the auth-file module
ban	Enable support for the mod_ban module
case	Enable support for the mod_case module
copy	Enable support for the mod_copy module
ctrls	Enable support for the mod_ctrls and mod_ctrls_admin modules
deflate	Enable support for the mod_deflate module
diskuse	Enable support for the mod_diskuse module
dso	Enable support for the mod_dso module
dynmasq	Enable support for the mod_dynmasq module, for dynamically updating MasqueradeAddress for dyndns-like scenarios)
exec	Enable support for the mod_exec module. WARNING: this could be a security risk
ident	Enable support for the mod_ident module
ifsession	Enable support for the ifsession module
ifversion	Enable support for the mod_ifversion module
linguas_bg_BG	Language support for bg_BG
linguas_fr_FR	Language support for fr_FR
linguas_it_IT	Language support for it_IT
linguas_ja_JP	Language support for ja_JP
linguas_ru_RU	Language support for ru_RU
log_forensic	Enable support for the mod_log_forensic module, log only suspicious actions.
memcache	Enable support for the mod_memcache module, for using memcached servers
msg	Enable support for the mod_msg module, allows system users to send messages to connected clients via the ftpdctl program.
qos	Enable support for the mod_qos module
ratio	Enable support for the mod_ratio module
readme	Enable support for the mod_readme module
rewrite	Enable support for the rewrite module
sftp	Enable support for the mod_sftp module and optionally mod_sftp_sql and mod_sftp_pam if matching USE flags are enabled
shaper	Enable support for the mod_shaper module
sitemisc	Enable support for the sitemisc module
softquota	Enable support for the quotatab module
trace	Build with trace support. Should not be enabled on production servers
unique_id	Enable support for the mod_unique_id module, every connection gets unique ID.
vroot	Enable support for the virtual root module

pure-ftpd

anondel	Permit anonymous to delete files
anonperm	Permit anonymous to change file permissions
anonren	Permit anonymous to rename files
anonres	Permit anonymous to resume file transfers
charconv	Enables charset conversion
implicittls	Enable TLS on Port 990
noiplog	Disables logging of IP addresses
paranoidmsg	Display paranoid messages instead of normal ones
resolveids	Resolve UIDs/GIDs
sysquota	Enables system quota support (needs sys-fs/quota)
vchroot	Enable support for virtual chroot (possible security risk)

yafc

ssh	Build with SFTP support

net-im

ayttm

irc	Enable Internet Relay Chat support
lj	Enable livejournal.com support
smtp	Adds support for sending messages via RFC2821 SMTP

bitlbee

libevent	Use libevent for event handling
nss	Use NSS for SSL support in MSN and Jabber
otr	Enable support for encrypted conversations
plugins	Enable support for plugins
purple	Use libpurple instead of the built-in IM protocol support
twitter	Enable Twitter protocol support

centerim

gadu	Enable support for the Gadu-Gadu protocol
irc	Enable support for the IRC protocol
lj	Enable support for the LiveJournal weblog system
otr	Enable encrypted conversations

choqok

attica	Build Open Collaboration Services plugin using dev-libs/libattica
konqueror	Build Konqueror Choqok plugin
telepathy	Enable support for the real-time communication framework telepathy

climm

otr	Enable encrypted conversations

corebird

glade	Install glade catalogs for corebird
spellcheck	Support spell checking

coturn

mongodb	Enable support for the mongodb database
redis	Enable support for the redis database

ejabberd

captcha	Support for CAPTCHA Forms (XEP-158) on registration
full-xml	Use XML features in XMPP stream (ex: CDATA), requires XML compliant clients
hipe	Compile natively with HiPE, not recommended
mssql	Enable Microsoft SQL Server support (via ODBC) for data storage
mysql	Enable MySQL support for data storage
nls	Enable character set conversion for mod_irc
odbc	Enable ODBC support to access data storage
postgres	Enable PostgreSQL support for data storage
redis	Enable Redis support for transient data
riak	Enable support for Riak - distributed NoSQL key-value data store
roster-gw	Turn on workaround for processing gateway subscriptions
sqlite	Enable SQLite database support
zlib	Enable Stream Compression (XEP-0138) using zlib

ekg2

gadu	Enable Gadu-Gadu protocol support (requires net-libs/libgadu).
gif	GIF token support for Gadu-Gadu protocol.
gnutls	Enable SSL/TLS support through GnuTLS for the plugins supporting it. If 'ssl' is enabled too, GnuTLS will be preferred where possible (and OpenSSL will be used elsewhere).
gpg	Enable jabber message encryption through app-crypt/gpgme.
jpeg	JPEG token support for Gadu-Gadu protocol.
minimal	Disable building extra plugins with no additional deps.
openssl	Support encryption in sim plugin, using OpenSSL.
oracle	Support logging messages into Oracle database.
sqlite	Support logging messages into SQLite3 database.
ssl	Enable the complete SSL/TLS support through OpenSSL. This also enables the 'sim' plugin which relies on OpenSSL.

empathy

gnome-online-accounts	Enable using net-libs/gnome-online-accounts for authorization (e.g. for Google Talk)
map	Enable world map support through media-libs/libchamplain

err

irc	Pull optional dependencies, needed for IRC backend
plugins	Enable support for installing plugins with dev-vcs/git

gajim

idle	Enable idle module
srv	SRV capabilities
xhtml	Enable XHTML support

jabberd2

experimental	Enable experimental features such as TLS Everywhere.
memdebug	Enable nad and pool debug. Requires USE="debug" to be set.
websocket	Enable WebSocket support on C2S port.

kadu

gadu	Enables Gadu communication protocol
mpd	Enables Music Player Daemon support
otr	Enable char encryption via OTR library
phonon	Enables phonon audio plugin
sdk	Install Kadu SDK (cmake module, API headers)
speech	Enables speech module

mcabber

aspell	Adds support for app-text/aspell spell checker.
otr	Enable encrypted conversations using Off-The-Records messaging

pidgin

gadu	Enable Gadu Gadu protocol support
groupwise	Enable Novell Groupwise protocol support
gstreamer	Enables voice and video sessions
gtk	Builds Pidgin, the GTK+ interface
meanwhile	Enable meanwhile support for Sametime protocol
ncurses	Build finch, console interface
prediction	Enable Contact Availability Prediction plugin
python	Build libgnt (GLib Ncurses Toolkit used by finch) with python scripting support
silc	Enable SILC protocol support
xscreensaver	Use X screensaver protocol extension to monitor idle/active status based on mouse/keyboard events
zephyr	Enable Zephyr protocol support

prosody

jit	Use LuaJIT instead of vanilla Lua
libevent	Use libevent for event handling
zlib	Support for compressing XMPP streams with mod_compression

psi

aspell	Enable spellchecking using app-text/aspell
enchant	Enable spellchecking using app-text/enchant
extras	Enable Psi+ patcheset
hunspell	Enable spellchecking using app-text/hunspell
iconsets	Install additional iconsets, some of them has not clear licensing
sql	Enable psi-new-history extras patch
webengine	Use dev-qt/qtwebengine instead of dev-qt/qtwebkit
webkit	Enable themed, html-based chatlogs
whiteboarding	Enable experimental interactive SVG drawing

pyaim-t

webinterface	Install dependencies needed for the web interface

pyicq-t

webinterface	Install dependencies needed for the web interface

qtox

X	Adds support for X11
gtk	Adds support for GTK and Status Notifier tray backends

skypeforlinux

pax_kernel	Triggers a paxmarking of the main skype binary

telepathy-connection-managers

gadu	Enable Gadu Gadu protocol support.
irc	Enable Internet Relay Chat (IRC) support.
meanwhile	Enable meanwhile support for Sametime protocol.
sip	Enable SIP/SIMPLE messaging and calling.
sipe	Enable Sip Exchange Protocol.
steam	Enable Steam Chat support.
xmpp	Enable XMPP protocol handler (this is also Google Talk).
yahoo	Enable Yahoo! messaging support.
zeroconf	Enable Link-Local Messaging via the zeroconf or Bonjour protocol.

tkabber

plugins	Enables installation the extra plugins

toxic

audio	Enables audio calling
notifications	Enables desktop notifications with libnotify, with sound support.
qrcode	Enables QR code support
video	Enables video calling

vacuum

adiummessagestyle	Use UI styles created for Adium
annotations	Enable adding comments to the contacts in the roster
aspell	Select app-text/aspell spell checker backend
autostatus	Change the status in accordance with the time of inactivity
avatars	Enable assigning and displaying avatars
birthdayreminder	Reminds about birthdays of your friends
bitsofbinary	Allow other modules to receive or send a small amount of binary data in XMPP stanza
bookmarks	Enable creating bookmarks of the Jabber conferences and Web pages
captchaforms	Perform tests for humanity outside of Web browser
chatstates	Post user's activity to the chat
clientinfo	Enable sending and receiving peer's application version, local time and last activity info
commands	Enable performing special commands provided by various services
compress	Compress stream of messages
console	Enable inspecting a raw XML stream
dataforms	Allow other modules to process and display data forms intended for the user
datastreamsmanager	Enable initiating a custom data stream between two XMPP entities
emoticons	Enable using smiley images in messages
enchant	Select app-text/enchant spell checker backend
filemessagearchive	Allows to save the history of conversations to local files
filestreamsmanager	Enable transferring files between two XMPP entities
filetransfer	Enable sending files to peers
gateways	Simplify the interaction with gateways to other IM systems
hunspell	Select app-text/hunspell spell checker backend
inbandstreams	Enable initiating in-band data stream between two XMPP enitites
iqauth	Enable logging on Jabber servers withous SASL authentication support
jabbersearch	Enable searching contacts in Jabber networks
messagearchiver	Enable saving the communication history both locally and on the server
messagecarbons	Allows to keep all user IM clients engaged in a conversation
multiuserchat	Enable Jabber multi-user conferences
pepmanager	Allows other plugins to recieve and publish PEP events
privacylists	Enable blocking the undesirable contacts
privatestorage	Allow other modules to store arbitrary data on the server
recentcontacts	Displays a recently used contacts
registration	Enable creating accounts in Jabber services
remotecontrol	Allows to remotely control the client
rosteritemexchange	Allows to exchange contact list items
rostersearch	Allows to search for contacts in the roster
servermessagearchive	Allows to save the history of communications on the server
servicediscovery	Enable receiving information about Jabber entities
sessionnegotiation	Enable initiating the session between two entities with setting the rules for XMPP stanzas exchange
shortcutmanager	Allows to setup user defined shortcuts
socksstreams	Enable initiating SOCKS5 data streams between two XMPP entities
urlprocessor	Allows other plugins to load data from custom types of URLs
vcard	Enable obtaining peer's personal contact information
xmppuriqueries	Allow other plugins to handle XMPP URI queries

net-irc

atheme-services

cracklib	Enable nickserv/cracklib module for enforcing strong account passwords
largenet	Enable support/tweaks for large networks
ldap	Enable ldap-backed authentication module
perl	Install a perl module which wraps around the services' XML-RPC interface

bip

freenode	Enables freenode-specific functionality. Currently that is only support for mute lists (MODE #channel +q).
noctcp	Disable the automatic CTCP VERSION reply which is often exploited by malicious people to cause a DoS (reconnect due to flooding).
oidentd	Enable oidentd support

epic5

archive	Use app-arch/libarchive to use zip and tar archives from scripts.
valgrind	Compile against dev-util/valgrind headers to improve memory-leak checking when running epic5 under valgrind.

hexchat

libcanberra	Enable sound event support using media-libs/libcanberra
libproxy	Enable proxy support.
plugin-checksum	Build Checksum plugin (needs plugins)
plugin-fishlim	Build FiSHLiM plugin (needs plugins )
plugin-sysinfo	Build SysInfo plugin (needs plugins)
theme-manager	Build the theme manager (mono)

inspircd

geoip	Add geoip support for country and city lookup based on IPs
gnutls	Enable TLS support
ipv6	Enable support for IP version 6
ldap	Enable LDAP support
mysql	Enable MySQL database backend
pcre	Adds support for Perl Compatible Regular Expressions
posix	Adds support for POSIX-compatible functions
postgres	Enable PostgreSQL database backend
sqlite	Enable Sqlite database backend
ssl	Enable SSL support
tre	Enable support for TRE, a lightweight, robust, and efficient POSIX compliant regexp matching library

iroffer-dinoex

admin	Compile with HTTP Admin
blowfish	Compile with blowfish encryption support
chroot	Compile with chroot support
http	Compile with HTTP server support
kqueue	Compile with kqueue() support
memsave	Compile with memory protection
telnet	Compile with Telnet server support

irssi

proxy	Adds support for a loadable IRC proxy module

kvirc

dcc_video	Support video connections over DCC protocol
phonon	Support Phonon for audio output

limnoria

crypt	Enables user authentication with GPG

ngircd

ident	Enables support for net-libs/libident

psybnc

multinetwork	Adds support for multiple networks
oidentd	Adds support for oidentd
scripting	Adds scripting support

quassel

X	Build the Qt5 GUI client for quassel. If this USE flag is disabled, the GUI is not built, and cannot be used. You might want to disable this on the server, but you need it enabled on the client.
breeze	Support the Breeze and Breeze-Dark icon sets (default for Plasma 5).
crypt	Support core->network per-channel and per-query blowfish encryption via app-crypt/qca SLOT 2.
dbus	Support desktop notifications via the StatusNotifier D-Bus service (used by most modern desktop environments).
monolithic	Build standalone client with integrated core, no external quasselcore needed. Only useful if you don't want to use Quassel's client/server model. The server and X flags are not needed in this case but it is possible to enable them too.
oxygen	Support the Oxygen icon set that was the default for KDE4.
phonon	Build client with phonon backend support. This enables sound playback in client.
server	Build the server binary. If this USE flag is disabled, the 'core' server binary for quassel is not built, and cannot be used. You need this enabled on the server, but you might want to disable it on the client.
snorenotify	Support for Snore notification framework.
urlpreview	Use QtWebEngine rendering engine for showing URL thumbnails.

rbot

aspell	Use aspell instead of ispell in the "spell" plugin for rbot. The vanilla plugin uses ispell, but enabling this flag makes it use the ispell interface from aspell instead.
cal	Add dependency over a package providing the /usr/bin/cal command, which is needed to enable the "cal" plugin for rbot. If the USE flag is disabled the plugin is also disabled by default.
figlet	Add dependency over app-misc/figlet, which is used by the "figlet" plugin for rbot. If the USE flag is disabled the plugin will be unable to use figlet; if toilet is also disabled, the plugin will be disabled.
fortune	Add dependency over games-misc/fortune-mod, which is needed to enable the "fortune" plugin for rbot. If the USE flag is disabled the plugin is also disabled by default.
host	Add dependency over net-dns/bind-tools (providing /usr/bin/host), which is needed to enable the "host" plugin for rbot. If the USE flag is disabled the plugin is also disabled by default.
nls	Build and install translation for the messages coming from the bot and its plugins (through dev-ruby/ruby-gettext).
shorturl	Add dependency over dev-ruby/shorturl, which is needed to enable the "shortenurl" plugin for rbot. If the USE flag is disabled the plugin is also disabled by default.
timezone	Add dependency over dev-ruby/tzinfo to enable the "time" plugin for rbot. If the USE flag is disabled the plugin is also disabled by default.
toilet	Add dependency over app-misc/toilet, which is used by the "figlet" plugin for rbot. If the USE flag is disabled the plugin will be unable to use toilet; if figlet is also disabled, the plugin will be disabled.
translator	Add dependency over dev-ruby/mechanize, which is needed to enable the "translator" plugin for rbot. If the USE flag is disabled the plugin is also disabled by default.

shadowircd

largenet	Enable support/tweaks for large networks

unrealircd

class-nofakelag	Enable an unsupported class::options flag called “nofakelag” allowing you to grant fakelag exemption to normal user (instead of just opers).
extban-stacking	Enable extended channel bans (such as +b ~c: and +b ~n:) to contain other extended bans instead of just hostmasks.
operoverride	Enable OperOverride extension
operoverride-verify	Enable requiring opers to invite themselves to +s/+p channels
prefixaq	Enable chanadmin and chanowner prefixes
showlistmodes	Display channel modes in /LIST (only configured at compiletime)
shunnotices	Enable notifying a user when un-shunned
topicisnuhost	Enable displaying nick!user@host as topic setter
usermod	Enable /set* and /chg* commands

weechat

alias	Enable plugin for alias control
buflist	Enable buflist plugin
charset	Enable encoding conversions
exec	Enable exec plugin
fifo	Enable FIFO support (sh pipes)
fset	Enable fast set plugin
irc	Enable IRC protocol support
logger	Enable support for logging
relay	Enable relay plugin (experimental)
scripts	Build infrastructure for scripting
trigger	Enable trigger plugin
xfer	Enable xfer plugin support

znc

daemon	Allow znc to run as a system-wide service. Installs an init script and creates a znc user:group.
zlib	Enable mod_deflate-like gzip support for znc's web interface using sys-libs/zlib.

net-libs

aqbanking

chipcard	Enable support for DDV/RSA-chipcards
ebics	Enable support for Electronic Banking Internet Communication Standard (EBICS)

axtls

cgi-lua	Enables lua backed cgi for axhttpd server
cgi-php	Enables php backed cgi for axhttpd server
httpd	Enables axhttpd web server component
static	Statically build axhttpd server

c-client

chappa	Enable Eduardo Chappa's patches for use with mail-client/alpine (mainly adds support for maildir)
doc	Install RFCs related to IMAP
topal	Enable support for net-mail/topal for use with mail-client/alpine

courier-authlib

vpopmail	Enable vpopmail support

cvm

vpopmail	Enable vpopmail support

daq

afpacket	Build the AFPacket data acquisition module. Functions similar to the PCAP module but with better performance. Snort can run unprivileged when using this module. AFpacket supports both inline and passive modes.
dump	Build the Dump data acquisition module. The dump DAQ allows you to test the various inline mode features available in 2.9 Snort like injection and normalization.
ipq	Build the IPQ data acquisition module. IPQ is the old way to process iptables packets for inline deployments. Snort can not run unprivileged when using this module.
nfq	Build the NFQ data acquisition module. NFQ is the new way to process iptables packets for inline deployments. Snort can not run unprivileged when using this module.
pcap	Build the PCAP data acquisition module.

glib-networking

gnome	Extract HTTP/HTTPS/SOCKS proxy configuration stored using GSettings
libproxy	Use net-libs/libproxy for getting the HTTP/HTTPS/SOCKS proxy configuration

gnome-online-accounts

gnome	Use gnome-base/gnome-control-center to set GNOME online accounts preferences

gnutls

dane	Build libgnutls-dane, implementing DNS-based Authentication of Named Entities. Requires net-dns/unbound
openpgp	Enable openpgp support
openssl	Build openssl compatibility libraries
pkcs11	Add support for PKCS#11 through app-crypt/p11-kit
sslv2	Support for the old/insecure SSLv2 protocol
sslv3	Support for the old/insecure SSLv3 protocol
test-full	Enable full test mode
tls-heartbeat	Enable the Heartbeat Extension in TLS and DTLS
tools	Build extra tools
valgrind	Enable usage of dev-util/valgrind in debug

gtk-vnc

gtk3	Build the gtk3 gtk-vnc library and other gtk3 assets

h323plus

aec	Enable acoustic echo cancellation
sound	Enable audio codecs
video	Enable video codecs

iax

snomhack	Use slower memset for SNOM phoneem

ldns

dane	Enable DNS-based Authentication of Named Entities (DANE) support
ecdsa	Enable ECDSA support
gost	Enable GOST support

libbitcoinconsensus

asm	Enable assembly for optimization
knots	Build enhanced Bitcoin Knots version, rather than Bitcoin Core

libbtbb

extras	Install pcapdump and btaptap tools
pcap	Add support for network packet capture via net-libs/libpcap
wireshark-plugins	Build the wireshark plugins for bluetooth baseband sniffing

libeXosip

srv	enable support for SRV records DNS queries

libesmtp

ntlm	Enable support for NTLM authentication

libetpan

liblockfile	Enable support for liblockfile library

libgsasl

gcrypt	Use dev-libs/libgcrypt for low-level crypto
ntlm	Add support for Microsoft's NTLM mechanism using net-libs/libntlm

libinfinity

server	Build and install the server binary including init.d/conf.d-scripts. Needed if you want to host an infinote server for gobby.

libisds

openssl	Use dev-libs/openssl as crypto backend instead of app-crypt/gpgme and dev-libs/libgcrypt

libmicrohttpd

epoll	use epoll() system call
messages	enable error messages

libnftnl

json	Supports parsing of JSON

libnids

glib	Use dev-libs/glib for multiprocessing support
libnet	Include code requiring net-libs/libnet

liboauth

bindist	Alias for the nss USE flag, since there are license compliancy trouble when using OpenSSL.
curl	If enabled, net-misc/curl is used thorugh the libcurl library; if it's not, the curl command is used instead. Some features are only available when using the library, but using it as library requires matching SSL implementations.
nss	Use Mozilla NSS (dev-libs/nss) as hash library; if this is disabled, dev-libs/openssl is used instead.

liboping

filecaps	Allow non-root users to use [n]oping utility.
ncurses	Build ncurses-based version of oping utility (requires sys-libs/ncurses)

libosmocore

embedded	Build for embedded use and disable unsupported features
pcsc-lite	Enable smartcard support with sys-apps/pcsc-lite

libpcap

netlink	Use dev-libs/libnl to put wireless interfaces in monitor mode.

libprotoident

tools	Build and install command-line tools

libproxy

gnome	Enable support for reading proxy settings from GNOME
kde	Enable support for reading proxy settings from KDE
spidermonkey	Use libmozjs from dev-lang/spidermonkey for PAC parsing
webkit	Use libjavascriptcoregtk from net-libs/webkit-gtk for PAC parsing

libqmi

mbim	Support QMI over Mobile Broadband Interface Model (MBIM)

libsoup

gssapi	Enable GSSAPI support
samba	Use net-fs/samba for NTLM Single Sign-On

libsrtp

aesicm	Use AES ICM cryptographic algorithm
console	Use /dev/console instead of stdout for error messages
openssl	Use OpenSSL crypto primitives
syslog	Use syslog for error messages

libssh

gcrypt	Prefer dev-libs/libgcrypt over dev-libs/openssl for encryption
gssapi	Enable gssapi support
pcap	Build with PCAP output support
server	Build with SSH server support
sftp	Build with SFTP support
ssh1	Build with SSH1 support

libssh2

gcrypt	Use dev-libs/libgcrypt instead of dev-libs/openssl

libtorrent-rasterbar

dht	Enable DHT (distributed hash table) support

libtrace

numa	Use sys-process/numactl

libupnp

blocking-tcp	Do not use async socket calls.
reuseaddr	Allow clean restarts by binding the socket with SO_REUSEADDR.
samples	Install sample applications.

libvncserver

24bpp	enable 24bpp support
gcrypt	enable support for gcrypt

libwebsockets

access-log	Support generating Apache-compatible access logs
cgi	Include CGI (spawn process with network-connected stdin/out/err) APIs
client	The client part of the library and libwebsockets-test-client
generic-sessions	With the Generic Sessions plugin
http-proxy	Support for rewriting HTTP proxying
http2	Support the HTTP/2 protocol
lejp	With the Lightweight JSON Parser
libev	Support event loops via dev-libs/libev
libuv	Support asynchronous I/O via dev-libs/libuv
server-status	Support json + jscript server monitoring
smtp	Provide SMTP support
sqlite3	Require SQLITE3 support

loudmouth

asyncns	Use net-libs/libasyncns for asynchronous name resolution.
openssl	Enable dev-libs/openssl support instead of gnutls (which is the default).

mbedtls

havege	Enable the HAVEGE random generator. Warning: the HAVEGE random generator is not suitable for virtualized environments
programs	Build PolarSSL programs

neon

libproxy	Add support for net-libs/libproxy
pkcs11	Add support for PKCS#11 using dev-libs/pakchois

nghttp2

hpack-tools	Install HPACK (header compression) helper tools
jemalloc	Use dev-libs/jemalloc for memory allocation
utils	Install nghttp, nghttpd and nghttpx

nodejs

inspector	Enable V8 inspector
npm	Enable NPM package manager
snapshot	Enable snapshot creation for faster startup
systemtap	Enable SystemTAP/DTrace tracing

ntirpc

gssapi	Include support for RPCSEC GSS
rdma	Include support for RDMA RPC

onion

boehm-gc	Add dev-libs/boehm-gc support for memory allocations.
libev	Use dev-libs/libev as thread poller instead of Linux's epoll.
libevent	Use dev-libs/libevent as thread poller instead of libev or Linux's epoll.
redis	Add support for redis sessions.

opal

celt	Enable CELT ultra-low delay audio codec
dtmf	Enable DTMF encoding/decoding support
fax	Enable T.38 FAX protocol
h224	Enable H.224 real time control protocol
h281	Enable H.281 Far-End Camera Control protocol
h323	Enable H.323 protocol
iax	Enable Inter-Asterisk eXchange protocol
ilbc	Enable iLBC (RFC 3951) speech codec
ivr	Enable Interactive Voice Response
lid	Enable Line Interface Device
plugins	Enable plugins support
sbc	Enable the Bluetooth low-complexity, SubBand Codec
sip	Enable Session Initiation Protocol
sipim	Enable SIP Instant Messages session
srtp	Enable Secure Real-time Transport Protocol
stats	Enable statistic reporting
swig	Use swig to generate bindings
video	Enable video support
vpb	Enable Voicetronics VPB card support
vxml	Enable VXML support
wav	Enable WAVFILE support
x264-static	Install x264 plugin statically linked with x264

ortp

ntp-timestamp	Turn on NTP timestamping on received packet
srtp	Add support for Secure RTP

phodav

spice	Install the spice-webdavd guest agent

pjproject

amr	Inlcude AMR codec in the build
epoll	Use /dev/epoll ioqueue on Linux (experimental)
g711	Include G.711 codecs in the build
g722	Include G.722 codec in the build
g7221	Include G.722.1 codec in the build
ilbc	Include iLBC codec in the build
l16	Include Linear/L16 codec family in the build
libyuv	Include libyuv in the build
openh264	Include Open H.264 support in the build
opus	Include OPUS support in the build
resample	Include resampling implementations in the build
silk	Include SILK support in the build
v4l2	Include Video4Linux v2 support in the build
webrtc	Enable WebRTC support

polarssl

havege	Enable the HAVEGE random generator. Warning: the HAVEGE random generator is not suitable for virtualized environments
programs	Build PolarSSL programs

ptlib

asn	Enable ASN decoding/encoding support
dtmf	Enable DTMF encoding/decoding support
http	Enable HTTP support
mail	Enable mail protocols (POP3/SMTP)
qos	Enable QOS support
remote	Enable remote connection support
serial	Enable serial port support
shmvideo	Enable shared memory video devices
socks	Enable SOCKS protocol support
stun	Enable STUN support
telnet	Enable telnet protocol support
tts	Enable Text-To-Speech server support
video	Enable video support
vxml	Enable VoiceXML support
wav	Enable WAVFILE support

qxmpp

opus	Enable Opus codec support via media-libs/opus
vpx	Enable VP8 codec support via media-libs/libvpx

rabbitmq-c

tools	Builds cli tools to interact with brokers

shairplay

alac	Add support for Apple Lossless Audio Codec files
static-libs	Build static versions of dynamic libraries as well
tools	Build and install a binary shairplay in /usr/bin

telepathy-qt

farstream	Enable support for audio/video calls via farstream

tox

av	Adds support for audio and video.
daemon	Enable the DHT Bootstrap Daemon.
log-debug	Log level: 4
log-error	Log level: 1
log-info	Log level: 3
log-trace	Log level: 5
log-warn	Log level: 2
no-log	Log level: 0 (no debug info logged)
ntox	Enable the testing nTox client.

udns

tools	Build and install dnsget, ex-rdns and rblcheck tools

wandio

http	Build support for reading files over HTTP using net-misc/curl

webkit-gtk

coverage	Enable code coverage support
egl	Enable EGL support
geoloc	Enable geolocation support through app-misc/geoclue
geolocation	Enable geolocation support through app-misc/geoclue
gles2	Enable GLESv2 support
nsplugin	Enable full nsplugin support (GTK2 plugins)
webgl	Build support for the WebGL HTML API using virtual/opengl

wvstreams

boost	Use dev-libs/boost to provide TR1-compatible functional interface. This USE flag is only needed with GCC earlier than version 4.1, or with other compilares not providing said interface.

xrootd

fuse	Enable the sys-fs/fuse filesystem driver
http	Enable http protocol support
rbd	Enable rados block device support via sys-cluster/ceph

zeromq

pgm	Build PGM (Pragmatic General Multicast)extention, a protocol for reliable multicast transport of data over IP networks.
sodium	Use dev-libs/libsodium for cryptography

net-mail

automx

memcached	Enable memcached support
sql	Enable support for SQL backends
tools	Install additional automx-test tool

courier-imap

trashquota	include deleted messages, and the Trash folder, in the estimated quota usage for maildirs

cyrus-imapd

backup	Enable backup service support
calalarm	Enable CalDAV alarm support
http	Enable http support
jmap	Enable JMAP support
lmdb	Enable support for using dev-db/lmdb
replication	Enable replication support
server	Enable building server binaries
sieve	Enable sieve support
sphinx	Enable Sphinx search engine support
xapian	Enable Xapian search engine support

dbmail

sieve	Enable sieve filter support

dovecot

argon2	Add support for ARGON2 password schemes
cydir	Add cydir storage support
imapc	Add imap client storage support
lucene	Add lucene full text search (FTS) support using dev-cpp/clucene
lz4	Add support for lz4 (de)compression
lzma	Add support for lzma (de)compression
managesieve	Add managesieve protocol support
mdbox	Add mdbox storage support
pop3c	Add pop3 client storage support
sdbox	Add sdbox storage support
sieve	Add sieve support
solr	Add solr full text search (FTS) support
textcat	Add libtextcat language guessing support for full text search (FTS)
vpopmail	Add vpopmail support

fdm

courierauth	Add support for Courier authentication library

fetchmail

hesiod	Enable support for hesiod
socks	Enable support for socks proxy
tk	Enable support for Tk GUI toolkit, in particular it installs fetchmailconf

gnubiff

password	Enable save passwords to connect mail servers in user space

hotwayd

smtp	Build SMTP proxy (hotsmtpd)

isync

compat	Enable legacy utilities

lbdb

abook	Enables app-misc/abook support
finger	Enables finger support

libpst

dii	enable dii support

mailutils

clients	Build client programs - frm maidag mail sieve messages readmsg dotlock movemail mimeview mh
kyotocabinet	Enable Kyoto Cabinet database support
servers	Build server programs - imap4d pop3d comsatd
tokyocabinet	Enable Tokyo Cabinet database support

mairix

gnus	Add support for the marks propagation feature in GNUS (provided by app-editors/emacs or app-xemacs/gnus for XEmacs users)

mpop

libsecret	Enable libsecret support to store login credentials

mu

emacs	Install the mu4e mail client.
gui	Build and install the experimental gui 'mug'.

notmuch

crypt	Support decryption and verification of PGP/MIME messages and in Emacs UI - encryption; support also S/MIME signature verification since version 0.22
doc	Install API documentation
emacs	Install Emacs UI (the main one)
mutt	Install helper script for Mutt
nmbug	Install experimental tag sharing / pseudo-bug-tracking script for Notmuch (see http://notmuchmail.org/nmbug/)
valgrind	Depend on dev-util/vagrind for test suite

offlineimap

sqlite	Enable runtime support for sqlite mail status backend.

qmailadmin

maildrop	Filter spam using maildrop

qpopper

apop	Enables the pop.auth file in /etc/pop.auth
mailbox	Enables mail spool file is in home directory ~/Mailbox

tpop3d

authexternal	Enable authentication by an external program
flatfile	Enable authentication against /etc/passwd-style flat files
passwd	Enable /etc/passwd authentication
sha1	Use OpenSSL for sha1 encrypted passwords.
shadow	Enable /etc/shadow authentication

uw-imap

clearpasswd	Enables cleartext logins outside of SSL sessions

vchkuser

debug	Enables debug messages to syslog

vpopmail

clearpasswd	Enables cleartext password storage in the vpasswd files
ipalias	Enables enable-ip-alias-domains
maildrop	Enables mail-filter/maildrop support in vdelivermail
spamassassin	Enables mail-filter/spamassassin support

net-misc

apt-cacher-ng

fuse	Install the sys-fs/fuse based acngfs, to use a userspace filesystem for the apt cache.

aria2

bittorrent	Enable support for the bittorrent protocol.
jemalloc	Use dev-libs/jemalloc to replace the malloc() implementation with a possibly faster one
libuv	Use dev-libs/libuv backend.
libxml2	Use dev-libs/libxml2 for XML parsing (preferred) instead of dev-libs/expat.
metalink	Enable support for metalink.
nettle	Use dev-libs/nettle and dev-libs/gmp for bittorrent/metalink crypto instead of dev-libs/libgcrypt (when dev-libs/openssl is not being used).
scripts	Install additional scripts which use aria2's xmlrpc functionality.
ssh	Enable SFTP support.

asterisk

cluster	Enable high-availability support through the Corosync Cluster Engine
dahdi	Support Digium compatible hardware (formerly known as Zaptel).
gtalk	Enable support for Google Talk services
http	Enable embedded web server
ilbc	Enable the Internet Low Bitrate Codec (iLBC)
newt	Include additional tools that require redhats windowing toolkit
osplookup	Support secure peering using the Open Settlement Protocol
pjproject	Enable support for pjproject (pjsip)
samples	Install sample sound and configuration files (default: on)
span	Enable support for the spandsp codec
srtp	Enable support for encrypted voice transmission (secure RTP)

asterisk-core-sounds

alaw	Install the sounds files for the alaw codec.
g722	Install the sounds files for the g722 codec.
g729	Install the sounds files for the g729 codec.
siren14	Install the sounds files for the siren14 codec.
siren7	Install the sounds files for the siren7 codec.
sln16	Install the sounds files for the sln16 codec.
ulaw	Install the sounds files for the ulaw codec.
wav	Install the sounds files for the wav codec.

asterisk-extra-sounds

alaw	Install the sounds files for the alaw codec.
g722	Install the sounds files for the g722 codec.
g729	Install the sounds files for the g729 codec.
gsm	Install the sounds files for the +gsm codec.
siren14	Install the sounds files for the siren14 codec.
siren7	Install the sounds files for the siren7 codec.
sln16	Install the sounds files for the sln16 codec.
ulaw	Install the sounds files for the ulaw codec.
wav	Install the sounds files for the wav codec.

asterisk-moh-opsound

alaw	Install the sounds files for the alaw codec.
g722	Install the sounds files for the g722 codec.
g729	Install the sounds files for the g729 codec.
gsm	Install the sounds files for the +gsm codec.
siren14	Install the sounds files for the siren14 codec.
siren7	Install the sounds files for the siren7 codec.
sln16	Install the sounds files for the sln16 codec.
ulaw	Install the sounds files for the ulaw codec.
wav	Install the sounds files for the wav codec.

batman-adv

bla	B.A.T.M.A.N. bridge loop avoidance
dat	B.A.T.M.A.N. distributed arp table
mcast	B.A.T.M.A.N. multicast optimizations
nc	B.A.T.M.A.N. network coding

bfgminer

adl	Enable support for controlling fans and overclocking on AMD cards with AMD Display Library
antminer	Enable support for mining with AntMiner U1 sticks
avalon	Enable support for mining with Avalon 1 ASIC modules
avalonmm	Enable support for mining with Avalon 2/3 ASIC modules
bfsb	Enable support for mining on BFSB host Raspberry Pi
bfx	Enable support for mining with BFx2 USB sticks
bifury	Enable support for mining with Bi*fury USB sticks
bigpic	Enable support for mining with Big Picture Mining USB sticks (Red/BlueFury, BF1, etc)
bitforce	Enable support for mining with ButterFly Labs BitFORCE ASICs and/or FPGAs
bitfury	Enable support for mining with 55nm Bitfury-based devices
cointerra	Enable support for mining with CoinTerra TerraMiner.
cpumining	Enable support for mining with CPUs
drillbit	Enable support for mining with Drillbit boards
dualminer	Enable support for mining with DualMiner USB sticks
gridseed	Enable support for mining with 5-chip GridSeed orbs
hashbuster	Enable support for mining with HashBuster nano boards
hashbuster2	Enable support for mining with HashBuster micro boards
hashfast	Enable support for mining with HashFast devices
icarus	Enable support for mining with Icarus-compatible devices (including Block Erupter Sapphire ASICs)
jingtian	Enable support for mining on JingTian boards via SPI/GPIO
keccak	Enable support for mining with Keccak miners
klondike	Enable support for mining with Klondike USB miners
libusb	Use libusb
littlefury	Enable support for mining with LittleFury USB sticks
metabank	Enable support for mining on Metabank host Raspberry Pi
minion	Enable support for mining on minion chips via SPI (BlackArrow Prospero)
modminer	Enable support for mining with ModMiner FPGAs
nanofury	Enable support for mining with NanoFury USB sticks
opencl	Enable support for mining with OpenCL-capable devices (GPUs)
proxy	Enable support for virtual proxy device
proxy_getwork	Enable proxy support for getwork protocol (often used with Block Erupter Blades)
proxy_stratum	Enable proxy support for stratum protocol
rockminer	Enable support for mining with RockMiner devices
screen	Provide start-bfgminer.sh script to launch BFGMiner in app-misc/screen
scrypt	Enable support for scrypt mining algorithm
sha256d	Enable support for SHA256d mining algorithm
twinfury	Enable support for mining with Twinfury USB sticks
udev-broad-rules	Enable broader udev rules that may match non-mining devices
x6500	Enable support for mining with X6500 FPGAs
zeusminer	Enable support for mining with ZeusMiner units
ztex	Enable support for mining with Ztex FPGAs

cfengine

html	Install HTML documentation
libvirt	Enable support for virtual machine management through app-emulation/libvirt
masterfiles	Install the Masterfiles Policy Framework
qdbm	Use dev-db/qdbm as database backend
tests	Install test files
tokyocabinet	Use dev-db/tokyocabinet as database backend

cgminer

ants1	Enable support for Antminer S1 Bitmain
ants2	Enable support for Antminer S2 Bitmain
ants3	Enable support for Antminer S3 Bitmain
avalon	Enable support for Avalon ASICs
avalon-miner	Enable support for Avalon miner ASICs
avalon2	Enable support for Avalon2 ASICs
avalon4	Enable support for Avalon4 ASICs
avalon7	Enable support for Avalon7 ASICs
bab	Enable support for BlackArrow Bitfury
bflsc	Enable support for BFL ASICs
bitforce	Enable support for mining with ButterFly Labs BitFORCE FPGAs
bitfury	Enable support for mining with BitFury ASICs
bitmine_A1	Enable support for mining with Bitmine.ch A1 ASICs
blockerupter	Enable support for mining with BlockRupter ASICs
cointerra	Enable support for mining with Cointerra ASICs
drillbit	Enable support for mining with Drillbit BitFury ASICs
hashfast	Enable support for mining with Hashfast
hashratio	Enable support for mining with Hashratio
icarus	Enable support for mining with Icarus FPGAs
klondike	Enable support for mining with Klondik ASICs
knc	Enable support for mining with KnC miners
minion	Enable support for mining with BlackArrow Bitfury
modminer	Enable support for mining with ModMiner FPGAs
sp10	Enable support for Spondoolies SP10
sp30	Enable support for Spondoolies SP30

chrony

adns	Support for asynchronous DNS
cmdmon	Support for command and monitoring
html	Install HTML documentation
ntp	Support for the Network Time Protocol (NTP)
phc	Support for the PTP (Precision Time Protocol) Hardware Clock (PHC) interface
pps	Support for the Linux Pulse Per Second (PPS) interface
refclock	Support for reference clocks
rtc	Support for the Linux Real Time Clock interface

connman

ethernet	Enable ethernet support.
iptables	Use net-firewall/iptables as firewall.
l2tp	Use net-dialup/xl2tpd for L2TP VPN support.
nftables	Use net-firewall/nftables as firewall.
ofono	Use net-misc/ofono for telephony support.
openconnect	Use net-vpn/openconnect for VPN support.
openvpn	Use net-vpn/openvpn for openvpn support.
pptp	Use net-dialup/pptpclient for PPTP VPN support.
tools	Enable testing tools.
vpnc	Use net-vpn/vpnc for cisco VPN support.
wispr	Enable support for WISPr hotspot logins.

connman-gtk

openconnect	Support easier authentication to AnyConnect VPNs

crossbar

tor	include tor services connections support

csync

sftp	Enable sftp transfer support via net-libs/libssh

curl

http2	Enabled HTTP/2.0 support
metalink	Enable metalink support
rtmp	Enable RTMP Streaming Media support
ssh	Enabled SSH urls in curl using libssh2
ssl	Enable crypto engine support (via openssl if USE='-gnutls -nss')

dahdi

flash	Support (short) flash on FXS

dahdi-tools

ppp	Enables PPP/DAHDIRAS support

dhcp

client	Install the dhclient program
server	Install the dhcpd and dhcrelay programs

dhcpcd

embedded	Embed the definitions of dhcp options in the dhcpcd executable

dhcpcd-ui

gtk3	Add support for x11-libs/gtk+ (The GIMP Toolkit)

dropbear

bsdpty	Add support for legacy BSD pty's rather than dynamic UNIX pty's -- do not use this flag unless you are absolutely sure you actually want it
multicall	Build all the programs as one little binary (to save space)
shadow	Enable shadow password support

dropbox

librsync-bundled	Use bundled librsync library

electron-cash

audio_modem	Enable plugin to support Audio Modem
cli	Enables the CLI interface
cosign	Enable plugin to support multisig wallets between multiple Electrum clients
digitalbitbox	Enable plugin to support Digital Bitbox hardware wallet
email	Enable plugin to support emailing invoices
qrcode	Enable QR code scanning with media-gfx/zbar
sync	Enable plugin to sync wallet metadata across multiple Electrum clients
vkb	Enable plugin for virtual keyboard

electrum

audio_modem	Enable plugin to support Audio Modem
cli	Enables the CLI interface
cosign	Enable plugin to support multisig wallets between multiple Electrum clients
digitalbitbox	Enable plugin to support Digital Bitbox hardware wallet
email	Enable plugin to support emailing invoices
greenaddress_it	Enable plugin to verify GreenAddress.it instant transactions
qrcode	Enable QR code scanning with media-gfx/zbar
sync	Enable plugin to sync wallet metadata across multiple Electrum clients
trustedcoin_com	Enable plugin to use two-factor service by TrustedCoin.com
vkb	Enable plugin for virtual keyboard

electrum-ltc

audio_modem	Enable plugin to support Audio Modem
cli	Enables the CLI interface
cosign	Enable plugin to support multisig wallets between multiple Electrum clients
digitalbitbox	Enable plugin to support Digital Bitbox hardware wallet
email	Enable plugin to support emailing invoices
qrcode	Enable QR code scanning with media-gfx/zbar
sync	Enable plugin to sync wallet metadata across multiple Electrum clients
vkb	Enable plugin for virtual keyboard

eventd

libcanberra	Enable plugin for sounds via media-libs/libcanberra
libnotify	Enable plugin to relay events to notification daemon (Note: not required for local notifications via net-misc/eventd)
notification	Enable plugin to display on-screen notifications
purple	Enable plugin for IM notifications via libpurple
speech	Enable plugin for Text-To-Speech support
webhook	Enable plugin to send payloads to webhook handlers
websocket	Enable support for WebSocket protocol

fatrat

bittorrent	Use the bittorrent protocol via net-libs/libtorrent-rasterbar.

freerdp

client	Build client binaries
openh264	Enable H.264 support using media-libs/openh264
server	Build server binaries

gerbera

curl	Support YouTube and external media sources (e.g. internet radio)
ffmpegthumbnailer	Enable video thumbnail support with media-video/ffmpegthumbnailer
lastfm	Enable last.fm support
magic	Use libmagic to determine file types
mysql	Use dev-db/mysql as backend rather than SQLite3
protocol-extensions	Enable partial DLNA support
taglib	Use media-libs/taglib for reading files' metadata rather than id3lib

gnome-online-miners

flickr	Enable Flickr support

gsasl

gcrypt	Use dev-libs/libgcrypt for low-level crypto
ntlm	Add support for Microsoft's NTLM mechanism using net-libs/libntlm

guacamole-server

ssh	enable support for ssh connections
telnet	enable support for telnet connections

gwget

epiphany	Build epiphany extensions

hotot

chrome	Build chrome browser extension

htbinit

esfq	Add support for Enhanced Stochastic Fairness queueing discipline.

hylafaxplus

html	Convert faxes into html email
jbig	JBIG Fax Compression Support
mgetty	Receive faxes via serial port connections
pam	hfaxd authentication via PAM

icaclient

gstreamer010	Enable audio support via media-libs/gstreamer using SLOT 0.10

icecast

kate	Add karaoke and text encapsulation support for Ogg files
logrotate	Install support files for app-admin/logrotate?
yp	Build support for yp public directory listings

iputils

SECURITY_HAZARD	Allow non-root users to flood (ping -f). This is generally a very bad idea.
arping	Build and install arping -- tool for sending ARP requests to peers (see also net-analyzer/arping)
clockdiff	Build and install clockdiff -- tool for comparing clocks via ICMP packets
gcrypt	Use dev-libs/libgcrypt for md5 support
nettle	Use dev-libs/nettle for md5 support
openssl	Use dev-libs/openssl for md5 support
rarpd	Build and install rarpd -- server for handling RARP (reverse ARP) requests; generally only used by old systems
rdisc	Build and install rdisc -- server for the client side of the ICMP router discover protocol
tftpd	Build and install tftpd -- server for the Trivial File Transfer Protocol (see also net-ftp/tftp-hpa)
tracepath	Build and install tracepath -- tool for tracing network paths for discovering MTU values
traceroute	Build and install traceroute -- tool for tracing network paths (see also net-analyzer/traceroute)

kafka-bin

internal-zookeeper	Use bundled local zookeeper instance

kafkacat

json	Enable json support

kea

openssl	Use dev-libs/openssl instead of Botan
samples	Install sample configuration files

knock

server	Installs the knockd server daemon.

lcr

asterisk	net-misc/asterisk channel driver
gsm-bs	net-wireless/openbsc driver
gsm-ms	net-wireless/osmobb driver
gsmhr	Support for GSM HR codec using reference code (very slow)
misdn	net-misc/misdn driver
sip	SIP support
ss5	CCITT No. 5 support

libteam

zmq	Build witch net-libs/zeromq support

lldpd

cdp	Enable Cisco Discovery Protocol
dot1	Enable Dot1 extension (VLAN stuff)
dot3	Enable Dot3 extension (PHY stuff)
edp	Enable Extreme Discovery Protocol
fdp	Enable Foundry Discovery Protocol
graph	Create dot graphs in documentations
jansson	Enable JSON output via Jansson
lldpmed	Enable LLDP-MED extension
old-kernel	Enable compatibility with Linux kernel older than 2.6.39
sanitizers	Enable code instrumentation with selected sanitizers
snmp	Enable the use of SNMP
sonmp	Enable SynOptics Network Management

megatools

fuse	Enables support for the filesystem in userspace plugin through sys-fs/fuse.

memcached

slabs-reassign	Allow manual reassignment of memory slabs at the cost of slab optimizations.

minidlna

netgear	Enable netgear branding
readynas	Enable readynas branding

miniupnpd

igd2	Build for IGDv2 instead of an IGDv1
leasefile	Enable lease file.
pcp-peer	Enable support for PCP-PEER to allow NAT-PMP clients to mangle their packets.
portinuse	Check if a port is in use before allowing a NAT-PMP client to map it.
strict	Be more strict regarding compliance with UPnP specifications.

modemmanager

mbim	Enable MBIM modem protocol
qmi	Enable support for the QMI modem protocol used by devices with Qualcomm chipsets

mosh

client	Build network client
examples	Include example scripts
mosh-hardening	Enable compiler and linker options to frustrate memory corruption exploits
server	Build network server
ufw	Install net-firewall/ufw rule set
utempter	Include libutempter support

mulk

checksum	Enable checksum verification for Metalink from dev-libs/openssl
metalink	Enable support for media-libs/libmetalink

ncp

diet	Compile against dev-libs/dietlibc

netkit-bootparamd

libtirpc	Build against net-libs/libtirpc for RPC support

networkmanager

connection-sharing	Use net-dns/dnsmasq and net-firewall/iptables for connection sharing
consolekit	Use sys-auth/consolekit for session tracking
dhclient	Use dhclient from net-misc/dhcp for getting ip
dhcpcd	Use net-misc/dhcpcd for getting ip
elogind	Use sys-auth/elogind for session tracking
json	Enable JSON validation via dev-libs/jansson in libnm.
modemmanager	Enable support for mobile broadband devices using net-misc/modemmanager
nss	Use dev-libs/nss for cryptography
ofono	Use net-misc/ofono for telephony support.
ovs	Enable OpenVSwitch support
ppp	Enable support for mobile broadband and PPPoE connections using net-dialup/ppp
resolvconf	Use net-dns/openresolv for managing DNS information
teamd	Enable Teamd control support
wext	Enable support for the deprecated Wext (Wireless Extensions) API; needed for some older drivers (e.g. ipw2200, ndiswrapper)
wifi	Enable support for wifi and 802.1x security using net-wireless/wpa_supplicant

nextcloud-client

dolphin	Install the kde-apps/dolphin extension
nautilus	Install the gnome-base/nautilus extension
sftp	Enable sftp transfer support via net-libs/libssh
shibboleth	Build support for Shibboleth single sign-on

ntp

openntpd	Allow ntp to be installed alongside openntpd
parse-clocks	Add support for PARSE clocks
samba	Provide support for Samba's signing daemon (needed for Active Directory domain controllers)

ofono

atmodem	ETSI AT modem support.
bluetooth	Enable Bluetooth modem support using net-wireless/bluez.
cdmamodem	Enable CDMA modem support.
datafiles	Enable install configuration and data files.
dundee	Enable BlueTooth DUN deamon support.
isimodem	Enable PhoNet/ISI modem support.
phonesim	Enable phone Simulator support
provision	Enable GPRS provisioning support
qmimodem	Enable Qualcomm QMI modem support
tools	Enable testing tools

oidentd

masquerade	Enable support for masqueraded/NAT connections

olsrd

pud	Install the Node Position Update plugin

openntpd

libressl	Enable HTTPS TLS time constraint support using dev-libs/libressl

openssh

X509	Adds support for X.509 certificate authentication
bindist	Disable EC/RC5 algorithms in OpenSSL for patent reasons.
hpn	Enable high performance ssh
ldap	Add support for storing SSH public keys in LDAP
ldns	Use LDNS for DNSSEC/SSHFP validation.
livecd	Enable root password logins for live-cd environment.
ssh1	Support the legacy/weak SSH1 protocol
ssl	Enable additional crypto algorithms via OpenSSL

openvswitch

monitor	Build the Python and GUI dependent monitor applications

owncloud-client

dolphin	Install the kde-apps/dolphin extension
nautilus	Install the gnome-base/nautilus extension
sftp	Enable sftp transfer support via net-libs/libssh
shibboleth	Build support for Shibboleth single sign-on

pavuk

hammer	Turn on chunky/hammer mode (DoS) in pavuk: when specified, pavuk will include features to stress test web sites using an ultrahigh performancereplay mechanism

plowshare

view-captcha	View captcha with aview

ps3mediaserver

multiuser	Allow renderer customization per-user.
transcode	Install optional dependencies for transcoding support via media-video/mplayer
tsmuxer	Install optional dependencies for transcoding support via media-video/tsmuxer

ptpd

debug	Enable debugging informations
experimental	Enable experimental features
ntp	Enable NTPD cooperation
pcap	Require net-libs/libpcap to allow layer 2 (raw Ethernet) transport
slave-only	Enable slave only operation (remove master mode functionality)
snmp	Require net-analyzer/net-snmp to enable SNMP configuration
statistics	Enable compution of statistics

putty

gtk	Build the PuTTY client which requires x11-libs/gtk+:2. Otherwise only the CLI tools puttygen, plink, pscp and psftp will be built.

quagga

bgpclassless	Apply unofficial patch to enable classless prefixes for BGP. Patch and information to be found at http://hasso.linux.ee/doku.php/english:network:quagga
fpm	Enable Forwarding Plane Manager support
multipath	Enable multipath routes support for any number of routes
nhrpd	Build Next Hop Resolution Protocol daemon
ospfapi	Enable OSPFAPI support for client applications accessing the OSPF link state database
pam	Add support for PAM (via sys-libs/pam) to the Quagga Virtual Terminal Interface Shell (vtysh); if the readline USE flag is disabled, this flag is ignored
protobuf	Enable support for dev-libs/protobuf
readline	Enable support for sys-libs/readline to provide the Quagga Virtual Terminal Interface Shell (vtysh)
tcp-zebra	Enable TCP zserv interface on port 2600 for Zebra/protocol-daemon communication. Unix domain sockets are chosen otherwise

rancid-git

git	Enable git (version control system) support

rdesktop

kerberos	Enable CredSPP support + Kerberos authentication with net-libs/libgssglue
pcsc-lite	Enable smartcard support with sys-apps/pcsc-lite driver
xrandr	Enable XRandR window extension support

remmina

spice	Support connecting to SPICE-enabled virtual machines
ssh	Enable support for SSH/SFTP protocol; see also 'vte'
telepathy	Enable telepathy support

rsync

stunnel	Provide helper scripts for using rsync via >=net-misc/stunnel-4

rygel

tracker	Install dependencies for the tracker plugin
transcode	Install dependencies for transcoding support

scponly

gftp	Enables gFTP compatibility
logging	Enables SFTP logging compatibility
passwd	Enables passwd compatibility
quota	Enables quota compatibility
rsync	Enables rsync compatibility with potential security risks
scp	Enables scp compatibility with potential security risks
sftp	Enables SFTP compatibility
subversion	Enables Subversion compatibility with potential security risks
unison	Enables Unison compatibility with potential security risks
wildcards	Enables wildcard processing with potential security risks
winscp	Enables WinSCP 2.0 compatibility with potential security risks

seafile-client

shibboleth	Build support for Shibboleth single sign-on

sitecopy

rsh	This allows the use of rsh (remote shell) and rcp (remote copy) for authoring websites. sftp is a much more secure protocol and is preferred.
webdav	Enable WebDav (Web-based Distributed Authoring and Versioning) support. This system allows users to collaborate on websites using a web based interface. See the ebuild for an FAQ page. Enables neon as well to handle webdav support.

sks

optimize	Enables bytecode optimization

slimrat

X	Install also GUI client

spice-gtk

dbus	Support for desktop integration such as automounting and other APIs exposed by your DE via D-Bus
gstaudio	Using gstreamer backend as audio decodec support
gstvideo	Using gstreamer backend as video decodec support
gtk3	Link against x11-libs/gtk+:3 instead of x11-libs/gtk+:2
lz4	Enable support for LZ4 compression using app-arch/lz4
mjpeg	Enable builtin mjpeg video decoder
policykit	Enable sys-auth/polkit support for the usbredir acl helper
usbredir	Use sys-apps/usbredir to redirect USB devices to another machine over TCP
webdav	Support for folder-sharing between guest and client using net-libs/phodav

sshrc

mosh	Install Support for mosh

stargazer

debug	Enable extra debug codepaths, like asserts and extra output.
doc	Adds extra documentation (API, doc, etc).
examples	Install examples, usually source code.
module_auth_always_online	Enable build of "Always Online" authentication module for Stargazer.
module_auth_freeradius	Enable build of "Radius" authentication module for Stargazer. This module capable of using RADIUS procotol for user authentication.
module_auth_internet_access	Enable build of "InetAccess" authentication module for Stargazer. InetAccess is a Stargazer specific authentication protocol.
module_capture_ether	Enable build of "Ethernet" traffic capture module for Stargazer. This module uses RAW sockets to capture traffic.
module_capture_ipq	Enable build of "IPQ" traffic capture module for Stargazer. This module uses IPQ subsystem to capture traffic.
module_capture_netflow	Enable build of "NetFlow" traffic capture module for Stargazer. This module capable of receiving traffic data by NetFlow protocol.
module_config_rpcconfig	Enable build of "XMLRPC" configuration module for Stargazer. This module uses XML-RPC protocol for configuring Stargazer.
module_config_sgconfig	Enable build of "SGConf" configuration module for Stargazer. This module uses Stargazer specific protocol for configuring Stargazer.
module_other_ping	Enable build of "Ping" module for Stargazer. This module pings connected users from time to time to ensure they are alive.
module_other_remote_script	Enable build of "Remote Script" module for Stargazer. This module control rscriptd daemon over the net and makes it execute scripts in reaction to different Stargazer events.
module_other_smux	Enable build of SMUX module for Stargazer. This module uses SMUX protocol to provide various information about Stargazer.
module_store_files	Enable build of storage plugin for Stargazer based on plain files.
module_store_firebird	Enable build of storage plugin for Stargazer, which uses Firebird database for storage.
module_store_mysql	Enable build of storage plugin for Stargazer, which uses MySQL for storage.
module_store_postgres	Enable build of storage plugin for Stargazer, which uses PostgreSQL for storage.
radius	Enable build of FreeRADIUS module for data access via Stargazer.
rscriptd	Enable build of remote script execute daemon for Stargazer, which run scripts when receive special signal from Stargazer.
sgauth	Enable build of command-line utility for authorization in Stargazer.
sgconf	Enable build of command-line utility for configuring Stargazer.
sgconf_xml	Enable build of command-line xml-based utility for configuring Stargazer.
sgconv	Enable build of utility to convert Stargazer data between storage backends.
stargazer	Enable build of Stargazer billing system.
static-libs	Install static libraries.

streamtuner

shout	Enable shoutcast plug-in.
xiph	Enable xiph.org plug-in.

stunnel

stunnel3	Install the stunnel3 wrapper.

teamviewer

system-wine	Use app-emulation/wine instead of bundled wine.

termpkg

uucp	Adds support for uucp style device locking

tigervnc

dri3	Build with DRI3 support
drm	Build with DRM support
server	Build TigerVNC server
xorgmodule	Build the Xorg module

trackma

cli	Enable cli version
ncurses	Enable curses version

uftp

server	Install uftp server daemon

vde

pcap	Enable the pcap-based plugin that allows creating a switch against a real interface.
ssl	Enable the cryptcab plugin that allows creating an encrypted virtual cable.

vinagre

spice	Enable access to SPICE-enabled virtual machines
ssh	Enable ssh plugin using x11-libs/vte
telepathy	Enable access to remote desktop via a net-libs/telepathy-glib client

vino

telepathy	Enable desktop sharing through a telepathy client

wget

ntlm	Enable support for NTLM (Windows-based) authorization
uuid	Generate UUIDs for the WARC (Web ARChive file format) using libuuid; otherwise use a simple RNG (random number generator)

wicd

ambiance	Install icons from Ubuntu's ambiance theme
gnome-shell	Install gnome-shell extension
gtk	Installs a gtk UI. This is enabled by default because it is intended behavior. Requires dev-python/pygtk
ioctl	Installs additional python libraries to use as a backend. This will improve speed but is experimental.
mac4lin	Change default icons to mac4lin icon set
ncurses	Installs a ncurses UI
pm-utils	Installs the pm-utils hooks for suspend/resume and requires sys-power/pm-utils

x2goserver

fuse	Use net-fs/sshfs to allow shared folders

youtube-viewer

gtk	Install the gtk GUI, called gtk-youtube-viewer

net-nds

389-ds-base

auto-dn-suffix	Enable auto bind with auto dn suffix over unix domain socket (LDAPI) support
autobind	Enable auto bind over unix domain socket (LDAPI) support
bitwise	Enable bitwise plugin - supported data in raw/bitwise format
dna	Enable dna (distributed numeric assignment ) plugin - to automatically assign unique uid numbers to new user entries as they are created.
ldapi	Enable LDAP over unix domain socket (LDAPI) support
pam-passthru	Enable pam-passthru plugin - for simple and fast system services used in ldap
presence	Enable presence plugin - non-standard syntax validation

gosa-core

mail	Manage mail accounts and servers with gosa.
samba	Manage samba accounts with gosa.

ldapvi

gnutls	Use net-libs/gnutls instead of dev-libs/openssl

nsscache

nsscache	Depend on sys-auth/libnss-cache to handle flat files
nssdb	Depend on sys-libs/libnss_db to handle dbm files.

openldap

experimental	Enable experimental backend options
kinit	Enable support for kerberos init
minimal	Build libraries & userspace tools only. Does not install any server code
odbc	Enable ODBC and SQL backend options
overlays	Enable contributed OpenLDAP overlays
pbkdf2	Enable support for pbkdf2 passwords
sha2	Enable support for pw-sha2 password hashes
smbkrb5passwd	Enable overlay for syncing ldap, unix and lanman passwords

rpcbind

warmstarts	Enables rpcbind to cache configuration for warm restarts

tac_plus

finger	Adds support for checking user counts via fingering the NAS
maxsess	Enforce a limit on maximum sessions per user

net-news

rssguard

webengine	Use dev-qt/qtwebengine for embedded web browser

net-nntp

inn

innkeywords	Enable automatic keyword generation support
inntaggedhash	Use tagged hash table for history (disables large file support)

nzbget

parcheck	Enable support for checking PAR archives

sabnzbd

7za	Add support for extracting 7za files
rar	Add support for extracting rar files
unzip	Add support for extracting zip files

slrn

canlock	Add support for cancel locks via net-libs/canlock
uudeview	Add support for yEnc coding and more using dev-libs/uulib

tin

cancel-locks	Enable Cancel-Lock header functionality (also enables USE=evil)
etiquette	Enable the display off posting etiquettes
evil	Let tin generate a message ID
forgery	Cancel messages posted from a different account
gpg	Enable app-crypt/gnupg support

net-p2p

airdcpp-webclient

nat-pmp	Enable support for the NAT-PMP protocol
tbb	Enable support of the TBB library to improve performance
webui	Enable the Web UI

amule

daemon	Enable amule daemon
remote	Enable remote controlling of the client
stats	Enable statistic reporting

bitcoin-cli

knots	Build enhanced Bitcoin Knots version, rather than Bitcoin Core
ljr	Enable Luke Dashjr's patches

bitcoin-qt

asm	Enable assembly for optimization
bip70	Enable support for the BIP70 payment protocol
bitcoin_policy_rbf	Replace By Fee policy: Your node will preferentially mine and relay transactions paying the highest fee, regardless of receive order
bitcoin_policy_spamfilter	Enhanced spam filter policy: Notorious spammers will not be assisted by your node
http	Enable support for the JSON-RPC and REST HTTP server (builtin net-p2p/bitcoind)
knots	Build enhanced Bitcoin Knots version, rather than Bitcoin Core
libevent	Use dev-libs/libevent
ljr	Enable Luke Dashjr's patches
qrcode	Enable generation of QR Codes for receiving payments
tor	Enable automatic configuration of a Tor hidden service
upnp	Enable Universal Plug and Play
wallet	Enable wallet support
zeromq	Report blocks and transactions via zeromq

bitcoind

asm	Enable assembly for optimization
bitcoin_policy_rbf	Replace By Fee policy: Your node will preferentially mine and relay transactions paying the highest fee, regardless of receive order
bitcoin_policy_spamfilter	Enhanced spam filter policy: Notorious spammers will not be assisted by your node
knots	Build enhanced Bitcoin Knots version, rather than Bitcoin Core
ljr	Enable Luke Dashjr's patches
upnp	Enable Universal Plug and Play
wallet	Enable wallet support
zeromq	Report blocks and transactions via zeromq

datacoin-hp

logrotate	Use app-admin/logrotate for rotating logs

dbhub

switch_user	Enable support for switching user

deluge

console	Enable default console UI
linguas_iu	Inuktitut locale
linguas_nap	Neapolitan locale
linguas_pms	Piemontese locale
webinterface	Install dependencies needed for the web interface

dogecoin-qt

qrcode	Enable generation of QR Codes for receiving payments

eiskaltdcpp

cli	Enable sample cli based on readline
daemon	Enable eiskaltdcpp-daemon
dht	Enable DHT (distributed hash table) support for libeiskaltdcpp
json	Enable JSON for cli and daemon
libcanberra	Enable sound notifications support over libcanberra in EiskaltDC++ Gtk
minimal	Don't install headers

fms

frost	Add support for frost boards

go-ethereum

devtools	Build Ethereum development tools (evm, abigen, puppeth, ...)
opencl	Add OpenCL GPU mining support

go-ipfs-bin

fuse	Enable runtime support for sys-fs/fuse

ktorrent

bwscheduler	Schedule upload and download limits over a period of a week
downloadorder	Specify the download order of a multi-file torrent
infowidget	Displays general information about a torrent in several tabs
ipfilter	Filter IP addresses through a blocklist
kross	Enable kross scripting support
logviewer	Displays the logging output
magnetgenerator	Generates magnet URI's
mediaplayer	Phonon-based media player
rss	Syndication plugin for KTorrent, supporting RSS and Atom feeds
scanfolder	Scan folders for torrent files and load them
search	Search for torrents
shutdown	Shutdown when done
stats	Shows statistics about torrents in several graphs
upnp	Forward ports using UPnP
zeroconf	Discover peers on the local network using the Zeroconf protocol

litecoind

logrotate	Use app-admin/logrotate for rotating logs
wallet	Enable wallet support

mldonkey

bittorrent	enable bittorrent support
fasttrack	enable fasttrack support
gnutella	enable gnutella and gnutella2 support
guionly	enable client build only
magic	enable use of libmagic

ppcoind

logrotate	Use app-admin/logrotate for rotating logs

primecoin-qt

qrcode	Enable generation of QR Codes for receiving payments

primecoind

logrotate	Use app-admin/logrotate for rotating logs

pybitmessage

opencl	Uses dev-python/pyopencl for GPU acceleration.

qbittorrent

webui	Enable the Web UI

retroshare

cli	Enables the CLI version of RetroShare
feedreader	Enables the Feedreader plugin
gnome-keyring	Enables potentially insecure autologin capability via Gnome Keyring
gui	Enables the GUI version of RetroShare
voip	Enables VOIP plugin

rtorrent

daemon	Uses app-misc/screen to daemonize this application

syncthing

tools	Install stdiscosrv, strelaysrv and other tools to /usr/libexec/syncthing/.

transmission

lightweight	Optimize transmission for low-resource systems (smaller cache size, prefer unencrypted peer connections, etc.)
mbedtls	Use mbed TLS instead of OpenSSL
xfs	Enable XFS filesystem capabilities by using sys-fs/xfsprogs headers (in building of fdlimit(.c))

transmission-remote-gtk

libproxy	Use net-libs/libproxy for getting the HTTP/HTTPS/SOCKS proxy configuration.

tribler

vlc	Enable vlc support.

xmr-stak

cuda	Enable NVIDIA CUDA toolkit support
devfee	Enable payment of devfee to the developer
hwloc	Enable CPU affinity support via hwloc
opencl	Enable OpenCL support
webserver	Enable internal webserver

net-print

cups

java	Add support for the Java interpeter in the web server CGIs.
lprng-compat	Do not install lp... binaries so cups and lprng can coexist.
python	Add support for the Python interpeter in the web server CGIs.

cups-filters

foomatic	Build the included foomatic-rip printer driver. Strongly recommended.
ipp_autosetup	Let cups-browsed automatically set up IPP network printers by default.
pclm	Enable PCLm support

fax4cups

efax	Install net-misc/efax backend
hylafax	Install net-misc/hylafax backend
mgetty-fax	Install net-dialup/mgetty backend

hplip

X	Enables scanner GUI dependencies with USE="scanner" where media-gfx/xsane is preferred over media-gfx/sane-frontends
fax	Enable fax on multifunction devices which support it
hpcups	Build the hpcups driver for cups (by HP)
hpijs	Build the IJS driver for cups (Foomatic)
kde	Enables kde-misc/skanlite as scanner GUI with USE="scanner X"
libusb0	Depend on virtual/libusb SLOT 0. Some old printers do not work with virtual/libusb SLOT 1.
minimal	Only build internal hpijs/hpcups driver (not recommended at all, make sure you know what you are doing)
parport	Enable parallel port for devices which require it
scanner	Enable scanner on multifunction devices which support it
snmp	Add support for net-analyzer/net-snmp which enables this driver to work over networks (both for server and client)
static-ppds	Use statically-generated PPDs instead of Dynamic PPDs. Although this is deprecated some printers may still need it to work properly. Use this flag if hp-setup fails to find/create a valid PPD file

kyocera-1x2x-mfp-driver

rastertokpsl-fix	Use custom wrapper script to sanitize arguments before passing to 'rastertokpsl' filter program

magicfilter

lprng-failsafe	Refuse options for compability with certain LPRng versions.

net-proxy

haproxy

51degrees	Device Detection using 51 Degrees
device-atlas	Use dev-libs/device-atlas-api-c library
net_ns	Enable network namespace support (CONFIG_NET_NS)
pcre-jit	Use JIT support for PCRE
pcre2	Enable PCRE2 RegEx support
pcre2-jit	Use JIT support for PCRE2
slz	Use dev-libs/libslz compression library
tools	Install additional tools (halog, iprange)
wurfl	Device Detection using WURFL

privoxy

client-tags	Enable support for client-specific tags
compression	Allow privoxy to compress buffered content before sending to the client, if it supports it
editor	Enable the web-based actions file editor
extended-host-patterns	Enable and require PCRE syntax in host patterns. You must convert action files to PCRE, see privoxy-url-pattern-translator.pl Use at your own risk!
external-filters	Allow to filter content with scripts and programs. Experimental
fast-redirects	Support fast redirects
force	Allow single-page disable (force load)
graceful-termination	Allow to shutdown Privoxy through the webinterface
ie-images	Enable a quick but not always reliable auto-detect whether requests from MS Internet Explorer are for an image or not
image-blocking	Allows the +handle-as-image action, to send "blocked" images instead of HTML
lfs	Support large files (>2GB) on 32-bit systems
png-images	Use PNG format instead of GIF for built-in images
stats	Keep statistics
toggle	Support temporary disable toggle via web interface
tools	Install log parser, regression tester and user agent generator tools
whitelists	Support trust files (white lists)
zlib	Use sys-libs/zlib to decompress data before filtering

rejik

banlists	Install upstream provided simple banlists

shadowsocks-libev

mbedtls	Use net-libs/mbedtls as crypto backend
openssl	Use dev-libs/openssl as crypto backend
system-libs	Use system libraries instead of the ones included in the upstream distribution

squid

ecap	Adds support for loadable content adaptation modules (http://www.e-cap.org)
esi	Enable ESI for accelerators, will cause squid reverse proxies to be capable of the Edge Acceleration Specification (www.esi.org)
htcp	Enable HTCP protocol
ipf-transparent	Adds transparent proxy support for systems using IP-Filter (only for *bsd)
kqueue	Enables *BSD kqueue() support
logrotate	Use app-admin/logrotate for rotating logs
pf-transparent	Adds transparent proxy support for systems using PF (only for *bsd)
qos	Adds support for Quality of Service using netfilter conntrack - see qos_flow directive for more info
ssl-crtd	Adds support for dynamic SSL certificate generation in SslBump environments
tproxy	Enables real Transparent Proxy support for Linux Netfilter TPROXY
wccp	Enable Web Cache Coordination Protocol
wccpv2	Enable Web Cache Coordination V2 Protocol

tinyproxy

filter-proxy	Enable filtering of domains/URLS
reverse-proxy	Enable reverse proxying
transparent-proxy	Enable transparent proxying
upstream-proxy	Enable upstream proxying
xtinyproxy-header	Include the X-Tinyproxy header

tsocks

dns	Force DNS queries to use SOCKS server via tcp
envconf	Allow TSOCKS_CONF_FILE to specify configuration file
server-lookups	Allow hostname resolution _for_ SOCKS servers
tordns	Apply tordns patch which allows transparent TORification of the DNS queries

ufdbguard

doc	Download and install the ufdbguard reference manual in PDF.
httpd	Build, install and start the provided mini-http daemon with the redirect CGI integrated. Since there is no way to tell ufdbguard to not start it, this is a build-time option.

net-voip

ekiga

h323	Enable H.323 protocol
shm	Enable the Shared Memory Extension from libXext

linphone

assistant	Turn on assistant compiling (needs gtk enabled)
gsm-nonstandard	Support non-standard GSM frequencies
sqlite	Turn on compilation of message storage
tools	Compile tools
video	Enable video support (display/capture)

telepathy-gabble

plugins	Enable plugin loader

yate

amrnb	use AMR-NB
dahdi	Enable Dahdi driver
gsm	use GSM codec
h323	use OpenH323
ilbc	Enable iLBC codec
ilbc-webrtc	Enable iLBC webrtc codec
isac-fixed	Enable iSAC fixed codec
isac-float	Enable iSAC float codec
mysql	use MySQL client library
postgres	use Postgress SQL
spandsp	use spandsp library
speex	use Speex codec
tdmcard	Enable TDMV API card driver
wanpipe	Enable Wanpipe support
wpcard	Enable Wanpipe card driver
zaptel	Enable Zaptel driver

net-vpn

badvpn

client	Build the badvpn-client program, a daemon that runs on endpoints of the VPN.
ncd	Build NCD, a lightweight scripting language especially suited for network configurations.
server	Build the badvpn-server program, a central server that manages the VPN network.
tun2socks	Build tun2socks, a program which implements a TUN device that forwards TCP traffic through a SOCKS5 server.
udpgw	Build udpgw, a small daemon which allows tun2socks to forward UDP traffic.

i2p

ecdsa	Enables additional checks to make sure a setup is available that is capable of using I2Ps ECDSA provisions. I2P will work without it, but you will likely see warnings.
nls	Adds Native Language Support using GNU gettext.

i2pd

i2p-hardening	Compile with hardening on vanilla compilers/linkers
websocket	Enable websocket server

ipsec-tools

hybrid	Makes available both mode-cfg and xauth support
idea	Enable support for the IDEA algorithm
nat	Enable NAT-Traversal
rc5	Enable support for the patented RC5 algorithm
stats	Enable statistics reporting

libreswan

dnssec	Use DNSSEC resolver (requires net-dns/unbound)

openconnect

gssapi	Build GSSAPI support
java	Build JNI bindings using jni.h
libproxy	Enable proxy support
lz4	Enable support for lz4 compression
stoken	Enable stoken support

openvpn

down-root	Enable the down-root plugin
iproute2	Enabled iproute2 support instead of net-tools
lz4	Enable LZ4 support
mbedtls	Use mbed TLS instead of OpenSSL
pkcs11	Enable PKCS#11 smartcard support
plugins	Enable the OpenVPN plugin system

pptpd

gre-extreme-debug	Log all GRE accepted packages when in debug mode (required if you want upstream support)

strongswan

constraints	Enable advanced X.509 constraint checking plugin
dhcp	Enable server support for querying virtual IP addresses for clients from a DHCP server. (IKEv2 only)
eap	Enable support for the different EAP modules that are supported
farp	Enable faking of ARP responses for virtual IP addresses assigned to clients (IKEv2 only)
gcrypt	Enable dev-libs/libgcrypt plugin which provides 3DES, AES, Blowfish, Camellia, CAST, DES, Serpent and Twofish ciphers along with MD4, MD5 and SHA1/2 hash algorithms, RSA and DH groups 1,2,5,14-18 and 22-24(4.4+). Also includes a software random number generator.
non-root	Force IKEv1/IKEv2 daemons to normal user privileges. This might impose some restrictions mainly to the IKEv1 daemon. Disable only if you really require superuser privileges.
openssl	Enable dev-libs/openssl plugin which is required for Elliptic Curve Cryptography (DH groups 19-21,25,26) and ECDSA. Also provides 3DES, AES, Blowfish, Camellia, CAST, DES, IDEA and RC5 ciphers along with MD2, MD4, MD5 and SHA1/2 hash algorithms, RSA and DH groups 1,2,5,14-18 and 22-24(4.4+) dev-libs/openssl has to be compiled with USE="-bindist".
pkcs11	Enable pkcs11 support
strongswan_plugins_blowfish	Enable support for the blowfish plugin
strongswan_plugins_ccm	Enable support for the ccm plugin
strongswan_plugins_ctr	Enable support for the ctr plugin
strongswan_plugins_gcm	Enable support for the gcm plugin
strongswan_plugins_ha	Enable support for the ha plugin
strongswan_plugins_ipseckey	Enable support for the ipseckey plugin
strongswan_plugins_led	Enable support for the led plugin
strongswan_plugins_lookip	Enable support for the lookip plugin
strongswan_plugins_ntru	Enable support for the ntru plugin
strongswan_plugins_padlock	Enable support for the padlock plugin
strongswan_plugins_rdrand	Enable support for the rdrand plugin
strongswan_plugins_systime-fix	Enable support for the systime-fix plugin
strongswan_plugins_unbound	Enable support for the unbound plugin
strongswan_plugins_unity	Enable support for the unity plugin
strongswan_plugins_vici	Enable support for the vici plugin
strongswan_plugins_whitelist	Enable support for the whitelist plugin

tinc

gui	Add GUI support, using dev-python/wxpython
uml	Enable support for User Mode Linux Sockets
vde	Enable Virtual Distributed Ethernet (VDE) based networking

tor

scrypt	Use app-crypt/libscrypt for the scrypt algorithm
tor-hardening	Compile tor with hardening on vanilla compilers/linkers
web	Build a tor2web service instead of a tor client
zstd	Use app-arch/zstd for compression

vpnc

resolvconf	Enable support for DNS managing framework net-dns/openresolv

wireguard

debug	Enable verbose debug reporting in dmesg of various WireGuard peer and device information.
module	Compile the actual WireGuard kernel module. Most certainly you want this enabled, unless you're doing something strange.
module-src	Install the module source code to /usr/src, in case you like building kernel modules yourself.
tools	Compile the wg(8) tool and related helpers. You probably want this enabled.

net-wireless

aircrack-ng

airdrop-ng	Build airdrop-ng
airgraph-ng	Build airgraph-ng
experimental	Build the "experimental" tools which may randomly fail to run properly
netlink	Use netlink for channel control instead of WEXT
unstable	Build the "unstable" tools which may randomly fail to run properly

bladerf

tecla	use libtecla for command line editing, tab completion, and history

bladerf-fpga

x115	bitstream for the x115KLE Cyclone IV FPGA bladerf model"
x40	bitstream for the x40KLE Cyclone IV FPGA bladerf model"

blueman

appindicator	Enable usage of dev-libs/libappindicator to export menu options
network	Add functionality to setup (host) PAN connections using either net-dns/dnsmasq or net-misc/dhcp
thunar	Install the sendto-plugin for xfce-base/thunar

bluez

deprecated	Build deprecated plugins
experimental	Build experimental plugins
extra-tools	Install tools that upstream doesn't install on purpose by default. All this tools shouldn't be used. Then, please notify upstream about you still need them to let them know the situation.
mesh	Add support for Bluetooth Mesh control application and advertising bearer.
obex	Enable OBEX transfer support.
test-programs	Install tools for testing of various Bluetooth functions
user-session	Allow compatibility with user-session semantics for session bus under systemd

chirp

radioreference	support downloading data from radioreference.com (premium users only)

crda

gcrypt	Use libgcrypt instead of openssl for key checking

gnuradio

analog	enable analog signal processing blocks
atsc	enable ATSC (HDTV) transmitter and receiver blocks
audio	enable blocks to connect to audio sources (mic-in) and sinks (speaker-out) ports on a computer
channels	enable channel mode blocks
digital	enable digital signal processing blocks
dtv	enable digital tv signal processing blocks
fcd	enable Funcube Dongle source block
fec	enable block for convolutional encoding using the CCSDS standard polynomial ("Voyager")
filter	enable filter signal processing blocks
grc	enable GNU Radio Companion graphical tool to design signal processing flow graphs
log	enable logging to console and files
noaa	enable NOAA POES HRPT receiver blocks
pager	enable pager signal processing blocks
performance-counters	enable block performance counters
trellis	enable trellis blocks for FSM
uhd	install UHD source and sink blocks
utils	install scripts to enable viewing and analysis of files produced by flow graphs
vocoder	enable blocks for audio voice encoders
wavelet	enable wavelet signal processing blocks
zeromq	enable zeromq message passing blocks

gqrx

gr-audio	Use audio support from net-wireless/gnuradio

gr-air-modes

fgfs	Support FlightGear
gui	Build the GUI
rtlsdr	Build with Realtek RTL2832U (rtlsdr) support
uhd	Build with Ettus Research USRP Hardware Driver support

gr-baz

armadillo	install MUSIC DOA estimator block
rtlsdr	install rtlsdr source block
uhd	install UHD aware blocks

gr-osmosdr

bladerf	Build with Nuand BladeRF support
fcd	Build with Funcube Dongle support
hackrf	Build with Great Scott Gadgets HackRF support
iqbalance	Enable support for I/Q balancing using gr-iqbal
mirisdr	Build with Mirics MSi2500 + MSi001 SDR support
rtlsdr	Build with Realtek RTL2832U (rtlsdr) support
uhd	Build with Ettus Research USRP Hardware Driver support

horst

pcap	Add support for network packet capture via net-libs/libpcap

hostapd

crda	Add CRDA support
logwatch	Install support files for sys-apps/logwatch
netlink	Adding support for using netlink to create VLANs
sqlite	Adding sqlite support
wps	Add support for Wi-Fi Protected Setup

kismet

client	Build the ncurses-based user interface
pcre	Build with pcre support
plugin-autowep	Build the autowep plugin
plugin-btscan	Build the btscan plugin
plugin-dot15d4	Build the dot15d4 plugin
plugin-ptw	Build the ptw plugin
plugin-spectools	Build the spectools plugin. This uses net-wireless/spectools
plugin-syslog	Build the syslog plugin.
ruby	Build extras which are written in ruby, example plugins and the like.
speech	Audio support using app-accessibility/flite
suid	Install a setuid root helper binary with limited functionality; this allows running kismet as a normal user, significantly reducing security risks

neard

tools	build and install extra helper utilities

openbsc

gprs	Support GPRS via OpenGGSN

osmocom-bb

transmit	Enable transmission capabilities.

pyrit

cuda	Enable CUDA support via net-wireless/cpyrit-cuda
opencl	Enable OpenCL support via net-wireless/cpyrit-opencl

spectools

debug	Build the raw output client for spectools. (for developers)
gtk	Build the gtk-2 based client for spectools
ncurses	Build the ncurses based client for spectools

ubertooth

bluez	use bluez to support clock following and scanning
pcap	Use libpcap for packet capture and read/write
specan	Enable the ubertooth spectrum analyzer
ubertooth1-firmware	Build/install ubertooth1-firmware

urh

hackrf	use native backend which directly uses net-libs/libhackrf
rtlsdr	use native backend which directly uses net-wireless/rtl-sdr
uhd	use native backend which directly uses net-wireless/uhd

wepattack

john	Build with app-crypt/johntheripper support

wireless-tools

multicall	Build the most commonly used tools as one binary

wpa_supplicant

ap	Add support for access point mode
eap-sim	Add support for EAP-SIM authentication algorithm
eapol_test	Build and install eapol_test binary
fasteap	Add support for FAST-EAP authentication algorithm
hs2-0	Add support for 802.11u and Passpoint for HotSpot 2.0
p2p	Add support for Wi-Fi Direct mode
privsep	Enable wpa_priv privledge separation binary
ps3	Add support for ps3 hypervisor driven gelic wifi
smartcard	Add support for smartcards
tdls	Add support for Tunneled Direct Link Setup (802.11z)
uncommon-eap-types	Add support for GPSK, SAKE, GPSK_SHA256, IKEV2 and EKE
wimax	Add support for Wimax EAP-PEER authentication algorithm
wps	Add support for Wi-Fi Protected Setup

yatebts

bladerf	Build bladeRF transceiver
rad1	Build RAD1 transceiver
uhd	Build UHD transceiver
usrp1	Build USRP1 transceiver

sci-astronomy

casacore

c++11	Build casacore using the C++11 standard
data	Installs measures and data (pulls sci-astronomy/casa-data)

cpl

gasgano	Enable support for sci-astronomy/gasgano file organizer

esomidas

libtirpc	Build against net-libs/libtirpc for RPC support

healpix

idl	Install healpix IDL/GDL routines

predict

xforms	Add a "map" client which uses the x11-libs/xforms library for its GUI
xplanet	Project predict data onto world maps generated by x11-misc/xplanet / x11-misc/xearth

psfex

plplot	Build with sci-libs/plplot to allow diagnostic plots during processing

scamp

plplot	Build with sci-libs/plplot to allow diagnostic plots during processing

sextractor

modelfit	Enable profile model fitting, needs sci-libs/atlas and sci-libs/fftw

stellarium

media	Enable sound and video support
sound	Enable sound support
stars	Install extra star catalogs

wcslib

fits	Enable support for the FITS format through sci-libs/cfitsio
pgplot	Builds PGBSOX routines, needs sci-libs/pgplot library
tools	Builds and installs extra command line utilities for WCS checking

sci-biology

abyss

misc-haskell	build abyss-samtobreak tool, pull in haskell toolchain

bioperl

db	Install sci-biology/bioperl-run
network	Install sci-biology/bioperl-run
run	Install sci-biology/bioperl-run

bowtie

tbb	Enables building bowtie with the Intel Threading Building Blocks from dev-cpp/tbb. This flag is recommended.

clustalw-mpi

mpi_njtree	Use MPI (as opposed to serial) code for computing neighbor-joining trees
static_pairalign	Use static (as opposed to dynamic) scheduling for pair alignments

exonerate

utils	Install all utilities

fasttree

double-precision	use double precision instead of single-precision floating point (2x memroy required)

goby

cpp	Compile C/C++ API

mcl

blast	Add support for NCBI BLAST data

plink

R	add support R language
webcheck	add support for online update checking every time the program starts

ucsc-genome-browser

server	Install genome browser Web application. If this flag is off, only libraries and utilities from the suite are installed.

yass

dmalloc	Enable debugging with the dmalloc library
lowmem	Build for environments with low amounts of memory

sci-calculators

datamash

openssl	Use dev-libs/openssl for cryptographic features

units

units_cur	Install the units_cur python script that updates currencies

sci-chemistry

PyMca

matplotlib	Support for plotting through matplotlib

apbs

fast	APBS fast mode (experimental)
fetk	Include support for FeTK
iapbs	C/C++/Fortran interface
tools	Install optional tools

avogadro

glsl	Enable glsl features via GLEW.

avogadro2

rpc	Enable RPC server
vtk	include vtk support

ball

cuda	Include cuda support
sql	Include SQL database support

chemtool

emf	EMF export support

cns

aria	Support patch for sci-chemistry/aria

eden

double-precision	More precise calculations at the expense of speed

ghemical

openbabel	Use sci-chemistry/openbabel for file conversions

gromacs

boost	Enable external boost library
cuda	Enable cuda non-bonded kernels
double-precision	More precise calculations at the expense of speed
hwloc	Enable HWLoc lib support
make-symlinks	Create symbolic links for pre-5.0 binary names
mkl	Use sci-libs/mkl for fft, blas, lapack routines
offensive	Enable gromacs partly offensive quotes
opencl	Enable opencl non-bonded kernels
single-precision	Single precision version of gromacs (default)
tng	Enable new trajectory format - tng

gsim

emf	Support for .emf export

jmol

client-only	Install the viewer only, no applet files for httpd

molequeue

client	Build the client application
server	Build the serve application
zeromq	Build with net-libs/zeromq support

mopac7

gmxmopac7	Add support library for gromacs

pdb2pqr

opal	Add web interface via opal
pdb2pka	Install experimental pdb2pka interface

pymol

web	Install Pymodule needed for web app support

raster3d

gd	libgd support for PNG and JPEG output

vmd

cuda	Use nvidia cuda toolkit for speeding up computations
gromacs	Add support for TNG file format
msms	Add support for MSMS SAS calcualtion tool
povray	Add support for povray raytracer for HQ images
tachyon	Add support for tachyon raytracer for HQ images

votca-csg

extras	Pull in extra applications from sci-chemistry/votca-csgapps
gromacs	Add support for gromacs file formats through sci-chemistry/gromacs

wxmacmolplt

flash	Add support for flash movie generation using media-libs/ming

sci-electronics

geda

stroke	enable mouse gesture support

gerbv

unit-mm	Set default unit for coordinates in status bar to mm

gspiceui

schematics	Use sci-electronics/geda for schematics editing
waveform	Use sci-electronics/gwave for waveform display

gtkwave

fasttree	Enables experimental Fast SST Tree widget code.
fatlines	Renders lines as double width in gtkwave.
judy	Enables Judy array support.
packed	Enables '#pragma pack' for data arrays (saves memory, costs time).

kicad

github	Add github support into PCB editor
i18n	Allow GUI internationalization through linguas_* use flags
minimal	Build only binaries without parts library and examples
python	Enable python scripting support

ngspice

shared	Build ngspice as a shared library

pcb

gcode	gcode file export
gif	GIF graphics export
jpeg	JPEG graphics export
m4lib-png	Enable creating png previews for the m4 library
nelma	NELMA file export
png	PNG graphics export
tk	Build tcl/tk graphical QFP footprint generator
toporouter	Build toporouter
xrender	Translucent PCB display for Motif/Lesstif GUI

pulseview

decode	Enable decoding of protocols while capturing

sigrok-cli

decode	Enable decoding of protocols while capturing

splat

hires	Builds additional high resolution application 'rfsplat-hd'

sci-geosciences

gdal-grass

postgres	Include support for dev-db/postgresql

gmt

gdal	Enable sci-libs/gdal library support
gmtfull	Full resolution bathymetry database
gmthigh	Add high resolution bathymetry database
gmttria	Non GNU triangulation method, more efficient
metric	Use SI (cm) units instead of US (inches) ones
mex	Enable compilation of mex supplement which requires Octave/Matlab
octave	Enable octave support

gpsbabel

gui	Enable the graphical user interface (requires dev-qt/qtwebengine)

gpsd

dbus	export gpsd data over dbus connections
latency_timing	support latency timing information
ntp	Enable net-misc/ntp shared memory interface and PPS kernel support for GPS time
shm	export gpsd over shared memory
sockets	export gpsd over unix sockets

grass

geos	Use sci-libs/geos for v.buffer and adds extended options to the v.select module
liblas	Include support for LAS and LAZ encoded LiDAR files through sci-geosciences/liblas
opencl	Enable OpenCL support

gshhs

data	Add earth data with sci-geosciences/gshhs-data

liblas

gdal	Add support for the sci-libs/gdal geospatial raster library
geotiff	Add support for geo-tagged TIFF files with sci-libs/libgeotiff

mapnik

gdal	Enable sci-libs/gdal library support

mapserver

gdal	Enable sci-libs/gdal library support
geos	Enable sci-libs/geos library support
postgis	Enable dev-db/postgis support
proj	Enable sci-libs/proj library support (geographic projections)
xslt	Enable xslt and exslt support xml-mapfile support

merkaartor

libproxy	Use net-libs/libproxy for getting the HTTP/HTTPS/SOCKS proxy configuration
webengine	Enable dev-qt/qtwebengine in some plugins

qgis

designer	Build custom widgets for dev-qt/designer
georeferencer	Determines whether georeferencer plugin should be built
grass	Add support for sci-geosciences/grass
mapserver	Determines whether mapserver should be built
polar	Enable support for the polar coordinate system via x11-libs/qwtpolar

viking

libexif	Use media-libs/libexif for EXIF support
magic	Use libmagic to determine mimetypes
mapnik	Enable a layer based on sci-geosciences/mapnik
sqlite	Enable MBTiles support based on dev-db/sqlite

xtide

gps	Use sci-geosciences/gpsd

sci-libs

ViSP

coin	Enables Coin3D support.
demos	Installs demo programs.
dmtx	Enables barcode data matrix support.
ogre	Enables dev-games/ogre support.
ois	Enables dev-games/ois support via ogre.
opencv	Enables media-libs/opencv support.
tutorials	Installs tutorials.
zbar	Enables barcodes reading.

adolc

sparse	Add support for sparse matrix algebra with sci-libs/colpack

armadillo

arpack	Link with sci-libs/arpack libraries for eigen decomposition
mkl	Use matrix allocation from the Intel MKL sci-libs/mkl
superlu	Use SuperLU for sparse linear equation solving sci-libs/superlu
tbb	Use matrix allocation from the Threads Building Blocks dev-cpp/tbb

arprec

qd	Use sci-libs/qd for quad-double datatype

atlas

generic	Build atlas assuming a fairly generic architecture (sse2 for x86, core2 for amd64)

avogadrolibs

static-plugins	Build all plugins statically into main plugin modules
vtk	include vtk support

cddlib

tools	Add a few executables and tests for cddlib

ceres-solver

c++11	Build ceres-solver using the C++11 standard
cxsparse	Enable simple support for sparse matrix algebra from sci-libs/cxsparse with no LAPACK dependencies
gflags	Use dev-cpp/gflags for flag parsing
schur	Enable fixed-size schur specializations (disable if binary size is an issue)
sparse	Enable support for sparse matrix algebra with various packages from SuiteSparse

cfitsio

tools	Build execs fpack, funpack, imcopy, fitscopy, listhead

cgnslib

legacy	Enable or disable building legacy code (3.0 compatible)
tools	A number of utility programs: cgnscheck, cgnscompress, cgnsdiff, cgnslist, cgnsnames, cgnsupdate, cgnsconvert, adf2hdf, hdf2adf.

chemkit

applications	Build also applications not only the libraries

cholmod

cuda	Use nvidia cuda toolkit for speeding up computations
metis	Enable the Partition module to cholmod using sci-libs/metis

clblas

client	Build a command line clBLAS client program.
ktest	A command line tool for testing single clBLAS kernel.
performance	Copy performance scripts that can measure and graph performance.

clblast

client	Enable compilation of the clients to test and compare performance with reference libraries

coinor-bonmin

glpk	Undocumented USE

coinor-clp

glpk	Enable GNU Linear Programming Kit sci-mathematics/glpk support
metis	Enable partitioning with sci-libs/metis
mumps	Enable sci-libs/mumps support
sparse	Enable support for sparse matrix with sci-libs/cholmod

coinor-osi

glpk	Enable GNU Linear Programming Kit sci-mathematics/glpk support

coinor-symphony

glpk	Enable GNU Linear Programming Kit sci-mathematics/glpk support

coinor-utils

glpk	Enable GNU Linear Programming Kit sci-mathematics/glpk support

dlib

cblas	Build with CBLAS virtual/cblas
cuda	Enable support for CUDA for Deep Neural Networks (cuDNN) on GPU (experimental)
mkl	Enable support for Intel FFT sci-libs/mkl

dmlc-core

s3	Support for the Amazon Simple Storage Service

fftw

float	Link default library to single precision instead of double (symlinks only and fftw-2.1)
quad	Build quadruple precision lib
zbus	Adds support for ZBus cycle-counter of mips

flann

cuda	Enable support for nVidia CUDA
octave	Add bindings for sci-mathematics/octave

gdal

armadillo	Use sci-libs/armadillo for faster TPS transform computation
aux_xml	Enable Portable Auxilliary Metadata generation
fits	Enable support for NASA's sci-libs/cfitsio library
geos	Add support for geometry engine (sci-libs/geos)
gml	Enable support for dev-libs/xerces-c C++ API
hdf5	Add support for the Hierarchical Data Format v5 (sci-libs/hdf5)
mdb	Enable support for Microsoft Access database
ogdi	Enable support for the open geographic datastore interface (sci-libs/ogdi)
opencl	Enable OpenCL support
spatialite	Enable Spatial DBMS over sqlite dev-db/spatialite
xls	Add the dev-libs/freexl library for xls import support

grib_api

aec	Build with Adaptive Entropy Coding compression, needs sci-libs/libaec
jasper	Use media-libs/jasper instead of media-libs/openjpeg for JPEG 2000 support

gsl

cblas-external	Link gsl with external cblas provided by (virtual/cblas) instead of shipped internal version
deprecated	Enable deprecated functions

hdf5

fortran2003	Enable new features that require Fortran 2003 (http://www.hdfgroup.org/HDF5/doc/fortran/NewFeatures_F2003.pdf)
hl	Enable high level API (https://support.hdfgroup.org/HDF5/doc/HL/index.html)

hypre

fei	Build the internal Finite Element Interface routines
int64	Build the 64 bits integer library

ipopt

hsl	hsl
mumps	Enable sci-libs/mumps support

lapack-reference

deprecated	Build deprecated routines

lemon

coin	Enable the sci-libs/coinor-clp and sci-libs/coinor-cbc graph algorithms
glpk	Enable GNU Linear Programming Kit sci-mathematics/glpk support
tools	Build additional tools

libccd

double	Use double precision floats.

libghemical

mopac7	Use sci-chemistry/mopac7 for semi-empirical calculations
mpqc	Use sci-chemistry/mpqc for quantum-mechanical calculations

libsc

romio	Build with support for the ROMIO MPI-IO component

libsigrok

ftdi	Enable drivers that need libftdi
parport	Enable drivers that are parallel (IEEE1284) based
serial	Enable drivers that are serial (RS232) based

libsvm

tools	Install python based tool scripts for data selection and visualization with sci-visualization/gnuplot

linux-gpib

firmware	Install firmware
isa	Build ISA kernel modules; from 3.12 on the setting is ignored and the decision based on the kernel configuration

lis

quad	Enable quadruple precision operations
saamg	Build the Smoothed Aggregation Algebraic MultiGrid preconditioner

magma

fermi	Compile for GPU NVIDIA Fermi family (2.x cards)
kepler	Compile for GPU NVIDIA Kepler family (GF 6xx cards)

mathgl

hdf	Add support for the Hierarchical Data Format v.4 sci-libs/hdf
octave	Add bindings for sci-mathematics/octave

matio

sparse	Extend formats for sparse matrix (not matlab)

mkl

fortran95	Installs the BLAS/LAPACK FORTRAN95 static libraries
int64	Installs the 64 bits integer libraries

mpir

cpudetection	Enables runtime cpudetection (useful for bindist, compatability on other CPUs)

mumps

metis	Enable matrix ordering with METIS (sci-libs/metis, sci-libs/parmetis)
scotch	Enable matrix ordering with sci-libs/scotch

netcdf

dap	Support for remote data access with the built-in OPeNDAP client
hdf	Add support for the Hierarchical Data Format v.4 sci-libs/hdf
tools	Build the utilities nccopy, ncgen and ncdump

nlopt

octave	Add plugin for sci-mathematics/octave

o2scl

armadillo	Build matrix manipulation with sci-libs/armadillo
eigen	Build matrix manipulation with dev-cpp/eigen

octomap

dynamicEDT3D	Build and install dynamicEDT3D library: A library for incrementally updatable Euclidean distance transforms in 3D.

opencascade

freeimage	Enable support for image i/o via media-libs/freeimage
gl2ps	Use gl2ps PostScript printing library
tbb	Enable multithreading with the Intel Threads Building Block dev-cpp/tbb
vtk	Enable Virtualisation Toolkit

openfoam

opendx	Install opendx visualisation tool
paraview	Enable support for paraview library
src	Install source files

orocos_kdl

models	Build models for some well known robots.

p4est

romio	Build with support for the ROMIO MPI-IO component
vtk-binary	Enable binary vtk output. If disabled vtk files will be written in ASCII text format.

pastix

int64	Build the 64 bits integer library
starpu	Build and link with dev-libs/starpu

pcl

cuda	Adds support for NVIDIA CUDA.
openni	Adds support for Kinect-like 3D sensors devices with dev-libs/OpenNI.
openni2	Adds support for Kinect-like 3D sensors devices with dev-libs/OpenNI2 (should be preferred over openni).
pcap	Adds pcap file capabilities in some drivers.
qhull	Adds convex-hull operation support via media-libs/qhull.
tutorials	Builds and installs tutorials.
vtk	Adds support for VTK-Visualizations.

plplot

dynamic	Build with dynamic drivers
octave	Add bindings for sci-mathematics/octave
pdl	Add bindings for dev-perl/PDL
qhull	Add bindings for media-libs/qhull
shapefile	Enable support for ESRI shapefiles

rtabmap

openni2	Adds support for Kinect-like 3D sensors devices with dev-libs/OpenNI2.

scikits_image

freeimage	Enable support for image i/o via media-libs/freeimage
pyamg	Enable support for algebraic solvers via dev-python/pyamg

scipy

sparse	Adds support for sparse solving with sci-libs/umfpack

scotch

int64	Build the 64 bits integer library (needed for > 2^31 vertices)
tools	Build and install extra exec tools

shogun

R	Enable support for dev-lang/R
octave	Enable support for sci-mathematics/octave
opencl	Enable support for building against OpenCL

silo

silex	Build silex data browser

spqr

metis	Use sci-libs/metis or sci-libs/parmetis for partitioning
tbb	Enable multithreading with the Intel Threads Building Block dev-cpp/tbb

spr

root	Add sci-physics/root graphics and i/o support

ssm

ccp4	Link superpose with libccp4

suitesparse

cuda	Enable nvidia cuda toolkit for speeding up computations
metis	Enable the Partition module to cholmod using sci-libs/metis
tbb	Enable multithreading with the Intel Threads Building Block dev-cpp/tbb

sundials

hypre	Build with sci-libs/hypre conditioners
sparse	Enable support for sci-libs/klu sparse solver
superlumt	Build with sci-libs/superlu_mt

superlu_mt

int64	Build the 64 bits integer library

symengine

arb	Add support for arb (sci-mathematics/arb)
benchmarks	Build benchmarks
boost	Add support for boost integers(dev-libs/boost)
flint	Add support for (sci-mathematics/flint)
llvm	Build with LLVM
mpc	Add support for multiprecision complex arithmetic(dev-libs/mpc)
mpfr	Add support for multiprecision floating point rouding(dev-libs/mpfr)

taucs

cilk	Enable multithreading using dev-lang/cilk

umfpack

cholmod	Use sci-libs/cholmod for matrix ordering

vtk

R	Enable support for dev-lang/R
all-modules	Build all modules
boost	Add support for boost
cg	Use nvidia's cg shaders
gdal	Support for gdal formated data
imaging	Building Imaging modules
json	Support for json formated data
kaapi	Use sci-libs/xkaapi to handle smp support
offscreen	Offscreen rendering through OSMesa
rendering	Building Redering modules
tbb	Use dev-cpp/tbb to handle smp support
views	Building Views modules
web	Install web component
xdmf2	Support for xdmf2 formated data

xkaapi

blas	Kaapi BLAS tasks for PLASMA
gpu	Build library for gpu threading

sci-mathematics

Macaulay2

optimization	Accept upstream's choices for -O option, i.e. -O3 almost everywhere.

agda

cpphs	Use cpphs instead of cpp.
stdlib	Install the standard library.
uhc	Add support for the uhc backend.

agda-stdlib

ffi	Install agda-lib-ffi for compilation using the MAlonzo backend

bertini

optimization	Accept upstream's choices for -O option.

cgal

mpfi	Enable support for multiple recision interval arithmetic via sci-libs/mpfi
ntl	Enable support for dev-libs/ntl

coq

camlp5	Build using camlp5. This is required for some plugins like Ssreflect.

cvc3

isabelle	Add integration support for the Isabelle/HOL theorem prover.
zchaff	Use the SAT solver zchaff whose copyright is owned by Princeton University and is more restrictive (see zchaff license).

e

isabelle	Add integration support for the Isabelle/HOL theorem prover.

flint

gc	Enable garbage collection support via dev-libs/boehm-gc
ntl	Build NTL interface

form

devref	Build and install developers reference
doxygen	Build and install API documentation

fricas

clisp	Add support for GNU CLISP (dev-lisp/clisp)
clozurecl	Add support for Clozure Common Lisp (dev-lisp/clozurecl)
cmucl	Add support for CMU Common Lisp (dev-lisp/cmucl)
ecls	Add support for Embeddable Common Lisp (dev-lisp/ecls)
gcl	Add support for GNU Common Lisp (dev-lisp/gcl)
sbcl	Add support for Steel Bank Common Lisp (dev-lisp/sbcl)

geomview

motionaveraging	Enable experimental motion averaging technique

gmp-ecm

custom-tune	Improve performance of some operations by selecting machine-specific defaults
gwnum	Use GWNum lib where possible

gretl

R	Enable support for dev-lang/R

gsl-shell

fox	Build a x11-libs/fox GUI

isabelle

graphbrowsing	Generate theory browsing information, including HTML documents that show a theory's definition, the theorems proved in its ML file and the relationship with its ancestors and descendants.
ledit	Use ledit for the isabelle tty line editor
readline	Use readline (rlwrap) for the isabelle tty line editor

kodkodi

isabelle	Add integration support for the Isabelle/HOL theorem prover.

maxima

clisp	Compile maxima with GNU CLISP (dev-lisp/clisp)
clozurecl	Compile maxima with Clozure Common Lisp (dev-lisp/clozurecl)
cmucl	Compile maxima with CMU Common Lisp (dev-lisp/cmucl)
ecls	Compile maxima with Embeddable Common Lisp (dev-lisp/ecls)
gcl	Compile maxima with GNU Common Lisp (dev-lisp/gcl)
sbcl	Compile maxima with Steel Bank Common Lisp (dev-lisp/sbcl)

minisat

extended-solver	Build extended version of SAT solver with additional features.

msieve

ecm	Enable support for the GMP-ECM library

normaliz

extras	Install sci-mathematics/Macaulay2 and sci-mathematics/singularpackages as shipped by upstream

nusmv

minisat	Enable support for MiniSat
zchaff	Enable support for zChaff

octave

glpk	Add support for sci-mathematics/glpk for linear programming
gui	Enable the graphical user interface
openssl	Use dev-libs/openssl for low level hash functions
qhull	Add support for media-libs/qhull, to allow `delaunay', `convhull', and related functions
qrupdate	Add support for sci-libs/qrupdatefor QR and Cholesky update functions
sparse	Add enhanced support for sparse matrix algebra with SuiteSparse

pari

data	Add additional data (elldata, galdata, seadata, nftables)

polymake

bliss	Enable sci-libs/bliss interface for graph and face lattice isomorphism computations.
cdd	Enable sci-libs/cddlib interface for convex hull computations (Should be kept enabled).
group	Build extension for dealing with permutation groups and symmetric objects.
libnormaliz	Build the bundled extension for lattice related computations.
libpolymake	Build the polymake library to build applications using the C++ interface.
lrs	Enable sci-libs/lrslib interface for convex hull computations.
ppl	Enable dev-libs/ppl interface for convex hull computations.
singular	Enable the interface to sci-mathematics/singular for ideal related computations.

rstudio

server	Build and install the RStudio server

rw

executable	Build the 'rw' program.

singular

boost	Compile against external boost headers (dev-libs/boost)

spass

isabelle	Add integration support for the Isabelle/HOL theorem prover.

unuran

prng	Use sci-mathematics/prng library
rngstreams	Use sci-mathematics/rngstreams library

why3-for-spark

coq	Add sci-mathematics/coq support
html	Build HTML documentation
hypothesis-selection	Enable hypothesis selection
profiling	Enable profiling
zarith	Use dev-ml/zarith
zip	Enable compression of session files

yacas

doc	Generate HTML documentation
gui	Build graphical interface for the native yacas engine. Requires Qt5
java	Build the Java yacas engine and text console for it
jupyter	Add support for jupyter notebook

yafu

sieve	Use msieve for the sieving steps of NFS

z3

isabelle	Add integration support for the Isabelle/HOL theorem prover.

sci-misc

boinc

cuda	Use nvidia cuda toolkit for speeding up computations. NOTE: works only for subset of nvidia graphic cards so make sure your card is supported before opening a bug about it.

h5utils

hdf	Build hdf to hdf5 (and vice-versa) converter
octave	Build Octave plugins

nco

dap	Support for remote data access with the NETCDF DAP client
ncap2	Build next generation netcdf arithmetic processor (needs dev-java/antlr)
udunits	Add sci-libs/udunits files support

sci-physics

bullet

bullet3	Build Bullet 3
double-precision	Build libraries in double precision
extras	Build additional libraries

cernlib-montecarlo

herwig	Build Herwig internal event generator, newer version available in sci-physics/herwig

espresso

cuda	Enable cuda support
examples	Installs the examples
packages	Installs extra TCL subpackages

fastjet

cgal	Use sci-mathematics/cgal instead of bundled algorithms
plugins	Build all standard and C++ plugins

geant

data	Add a lot of standard physics data files for geant4
dawn	Add support for media-gfx/dawn (3D postscript rendering)
gdml	Enable geometry markup language for xml
geant3	Add compatibility for geant321 to geant4
inventor	Add support for Open Inventor SGI toolkit via Coin3D
raytracerx	Enable raytracing for physics events
vrml	Enable output of geant4 in vrml formats

hepmc

cm	Build with cm instead of default mm for length units
gev	Build with GeV instead of default MeV for momentum units

herwig++

c++11	Build Herwig++ using the C++11 standard. Experimental feature, not for production use.
fastjet	Adds support for sci-physics/fastjet

hoomd-blue

cuda	Enable cuda non-bonded kernels

lammps

cuda	Enable cuda non-bonded kernels
lammps-memalign	Enables the use of the posix_memalign() call instead of malloc() when large chunks or memory are allocated by LAMMPS. Aliengnment is on 16 byte boundaries.

lhapdf

octave	Add bindings for sci-mathematics/octave

pythia

fastjet	Build jets using the sci-physics/fastjet package
hepmc	Adds support for High Energy Physics Monte Carlo Generators sci-physics/hepmc
lhapdf	Support the use of external PDF sets via sci-physics/lhapdf
root	Use sci-physics/root trees and histograms (in examples only)

root

R	Enable support for dev-lang/R
asimage	Enable support for media-libs/libafterimage
c++11	Build ROOT using the C++11 standard
c++14	Build ROOT using the C++14 standard
davix	Enable support for DAVIX Data Management Client (https://cern.ch/davix)
fits	Enable support for images and data from FITS files with sci-libs/cfitsio
fortran	Compile included Fortran programs
gdml	Enable GDML writer and reader
http	Enable http server support including but not limited to fastcgi support
jemalloc	Enable support for dev-libs/jemalloc
libcxx	Build ROOT against sys-libs/libcxx
math	Build all math related libraries plugins, needs sci-libs/gsl
memstat	Build memory statistics library, helps to detect memory leaks
minuit	Build ROOT's internal versions of minuit (fortran) and minuit2 (C++)
pythia6	Build the interface for sci-physics/pythia version 6.x
pythia8	Build the interface for sci-physics/pythia version 8.x
reflex	Build the reflection database for the C++ interpreter
roofit	Build RooFit function fitting package
root7	Build experimental features to be released with ROOT 7
shadow	Enable shadow authentication in rootd and proofd
table	Build libTable contrib library
tbb	Enable implicit multi-threading (IMT) with dev-cpp/tbb
tmva	Built TMVA (ROOT's multi-variate analysis toolkit for machine learning)
unuran	Enable support for sci-mathematics/unuran
vc	Enable support for dev-libs/vc with VecCore
xrootd	Build the interface for net-libs/xrootd

thepeg

c++11	Build ThePEG using the C++11 standard. Experimental feature, not for production use.
fastjet	Adds support for sci-physics/fastjet
hepmc	Adds support for High Energy Physics Monte Carlo Generators sci-physics/hepmc
lhapdf	Adds support for sci-physics/lhapdf
rivet	Adds support for sci-physics/rivet

yoda

c++11	Build using the C++11 standard
root	Adds support for sci-physics/root

sci-visualization

fityk

nlopt	Enable optimization with sci-libs/nlopt

gnuplot

bitmap	Enable dot-matrix printers and pbm terminal
compat	Enable backwards compatibility with version 4 syntax
gd	Add support for media-libs/gd. Needed for GIF, JPEG, and PNG image output.
libcerf	Enable special functions from sci-libs/libcerf

gwyddion

fits	Enable FITS image import via sci-libs/cfitsio
sourceview	Enable support for x11-libs/gtksourceview

labplot

cantor	Enable support for different open-source computer algebra systems via kde-apps/cantor
fits	Enable support for NASA's sci-libs/cfitsio library

opendx

cdf	Add support for sci-libs/cdf data exchange format
hdf	Add support for the Hierarchical Data Format (sci-libs/hdf)

paraview

boost	Enable the usage of dev-libs/boost
cg	Add support for nvidia's cg shaders
coprocessing	Enable the coprocessing infrastructure which is mainly useful in the context of clusters
development	Install development files including headers
nvcontrol	Add NVCONTROL support for OpenGL options
plugins	Build and install additional plugins

veusz

emf	Add FITS format via dev-python/pyemf
fits	Add FITS format via dev-python/astropy
minuit	Use Minuit during fitting viadev-python/pyminuit
vo	Add Virtual Observatory tools via dev-python/astropy

visit

cgns	Builds the reader for the CFD General Notation System file format.
silo	Adds support for reading .silo files.
xdmf2	Support for xdmf2 formated data.

yt

hub	Connect to the yt hub with dev-python/girder-client

sec-policy

selinux-base

open_perms	Enable the open permissions for file object classes (SELinux policy capability).
peer_perms	Enable the labeled networking peer permissions (SELinux policy capability).
ubac	Enable User Based Access Control (UBAC) in the SELinux policy
unconfined	Enable support for the unconfined SELinux module

selinux-base-policy

unconfined	Enable support for the unconfined SELinux policy module

sys-apps

accountsservice

elogind	Use sys-auth/elogind instead of sys-auth/consolekit for session tracking
systemd	Use sys-apps/systemd instead of sys-auth/consolekit for session tracking

baselayout

usrmerge	Activate the /usr merge when stages are built

busybox

make-symlinks	Create all the appropriate symlinks in /bin and /sbin.
math	Enable math support in gawk (requires libm)
mdev	Create the appropriate symlink in /sbin and install mdev.conf and support files
sep-usr	Support a separate /usr without needing an initramfs by booting with init=/ginit
static	Make the system rescue shell (/bin/bb) static so you can recover even when glibc is broken
systemd	Support systemd

coreutils

caps	Add Linux capabilities support in output of file utilities (ls, dir, ...) via sys-libs/libcap
hostname	Build the hostname program
kill	Build the kill program
multicall	Build all tools into a single `coreutils` program akin to busybox to save space

dbus

elogind	Use sys-auth/elogind for session tracking.
systemd	Build with sys-apps/systemd at_console support
user-session	Enable user-session semantics for session bus under systemd

dbus-broker

launcher	dbus-daemon compatibility launcher

debianutils

installkernel	Install /sbin/installkernel script (for Linux)

dstat

wifi	Enable wireless network functions

duc

X	Use X11 for the GUI instead of OpenGL. This is the recommended option
cairo	Build support for exporting to PNG and PDF with x11-libs/cairo
gui	Build support for a graphical client
leveldb	Use dev-libs/leveldb as the backend
ncurses	Build support for the ncurses client
sqlite	Use dev-db/sqlite:3 as the backend
tokyocabinet	Use dev-db/tokyocabinet as the backend

elfix

ptpax	Enable PT_PAX_FLAGS support.
xtpax	Enable XATTR_PAX_FLAGS support.

entropy-server

matter	Pull in app-admin/matter

etckeeper

bazaar	Support dev-vcs/bzr based repository
cron	Install cron script

firejail

apparmor	Enable support for custom AppArmor profiles
bind	Enable custom bind mounts
chroot	Enable chrooting to custom directory
contrib	Install contrib scripts
file-transfer	Enable file transfers between sandboxes and the host system
network	Enable networking features
network-restricted	Grant access to --interface, --net=ethXXX and --netfilter only to root user; regular users are only allowed --net=none
seccomp	Enable system call filtering
userns	Enable attaching a new user namespace to a sandbox (--noroot option)
x11	Enable X11 sandboxing

firejail-lts

seccomp	Enable system call filtering

flashrom

atahpt	Highpoint (HPT) ATA/RAID controller support
atapromise	Support for Promise PDC2026x (FastTrak/Ultra)
atavia	Support for VIA VT6421A SATA controllers
bitbang_spi	Bitbanging SPI infrastructure
buspirate_spi	Enable Bus Pirate SPI programmer
ch341a_spi	Enable WCH CH341A SPI programmer
dediprog	Dediprog SF100 support
drkaiser	Enable Dr. Kaiser programmer
dummy	Enable dummy tracing
ft2232_spi	Enable ftdi programmer, flashing through FTDI/SPI USB interface
gfxnvidia	Enable NVIDIA programmer
internal	Enable internal/onboard support
internal_dmi	Enable internal DMI decoding rather than use sys-apps/dmidecode
it8212	Support for ITE IT8212F ATA/RAID controllers
linux_spi	Enable support for Linux userspace spidev interface
mstarddc_spi	Support for SPI flash ROMs accessible through DDC in MSTAR-equipped displays
nic3com	Enable 3Com NIC programmer
nicintel	Support for Intel NICs
nicintel_eeprom	Support for EEPROMs on Intel Gigabit network cards
nicintel_spi	Support for SPI on Intel NICs
nicnatsemi	Support for National Semiconductor NICs
nicrealtek	Support for Realtek NICs
ogp_spi	Enable support for OGP (Open Graphics Project) SPI flashing
pickit2_spi	SUpport for SPI flash ROMs accessible via Microchip PICkit2
pony_spi	Enable support for SI-Prog like hardware by Lancos
rayer_spi	RayeR SPIPGM hardware support
satamv	Enable programmer for Marvell SATA controllers
satasii	Enable programmer for SiI SATA controllers
serprog	Enable Serial Flasher programmer
tools	Install additional tools
usbblaster	Enable support for Altera USB-Blaster dongles
usbblaster_spi	Enable support for Altera USB-Blaster dongles
wiki	Enable wiki informations, like supported devices etc.

fwupd

colorhug	Enable ColorHug support through x11-misc/colord package.
dell	Enable Dell-specific support.
elf	Enable libelf support through dev-libs/libelf package.
gpg	Enable GPG support.
man	Build and install man pages
uefi	Enable UEFI support
uefi_labels	Enable UEFI labels support

gawk

mpfr	use mpfr for high precision arithmetic (-M / --bignum)

gnome-disk-utility

fat	Include FAT16/FAT32 support (sys-fs/dosfstools)

hwdata-gentoo

binary-drivers	Adds support for ATI/NVIDIA binary drivers

hwids

net	Install the oui.txt and iab.txt databases
pci	Install the pci.ids database
udev	Install hwdb.d rules for udev
usb	Install the usb.ids database

hwloc

cuda	Enable CUDA device discovery
gl	Enable GL display device discovery (NVCtrl)
numa	Add support for numa memory allocation
pci	Enable PCI device discovery using libpci
plugins	Build hwloc components as plugins so that the hwloc core library does not directly depend on their dependencies (for instance the libpci library)

ibm-powerpc-utils

rtas	Add support for the Run Time Abstraction Services (RTAS)

iotools

make-symlinks	Generate sub-command symlinks to iotools -- note that a lot are simple like "xor"

ipmitool

openipmi	Use the system OpenIPMI implementation.

iproute2

berkdb	build programs that use berkdb (just arpd)
iptables	include support for iptables filtering
minimal	only install ip and tc programs, without eBPF support

irqbalance

numa	Support balancing IRQs across NUMA nodes

kexec-tools

booke	Include support for Book-E memory management
lzma	Enables support for LZMA compressed kernel images
xen	Enable extended xen support

kmod

lzma	Enable support for XZ compressed modules
tools	Install module loading/unloading tools.
zlib	Enable support for gzipped modules

linux-misc-apps

usbip	Include USB/IP binaries to replace net-misc/usbip

lm_sensors

contrib	Installs user contributed configuration files so you don't need to find settings on your own for your system if somebody else has already created such a configuration for sensors/mainboards you are using.
sensord	Enable sensord - a daemon that can be used to periodically log sensor readings from hardware health-monitoring chips

man-db

manpager	Enable manpager wrapper for colorizing output

mawk

forced-sandbox	Always enable -W sandbox mode for simpler/secure runtime

memtest86

serial	Compile with serial console support

memtest86+

floppy	Install a script to create floppy disks containing memtest86+ binaries.
iso	Compile an ISO image
serial	Compile with serial console support

moreutils

perl	Install scripts written in Perl

net-tools

arp	build the arp and rarp tools (for manipulating the ARP cache)
hostname	build the hostname and dnsdomainname tools
plipconfig	build the plipconfig tool (for working with old PLIP hardware)
slattach	build the slattach tool (for working with old serial ports)

nix

etc_profile	Install /etc/profile.d/ entry to inject nix support for all users.
gc	Enable garbage collection in the Nix expression evaluator (use dev-libs/boehm-gc).
sodium	Use dev-libs/libsodium for cryptography

openrc

netifrc	enable Gentoo's network stack (net.* scripts)
newnet	enable the new network stack (experimental)

pacman

doc	Install extended documentation using app-doc/doxygen. (Man pages are included by default.)
gpg	Enable GPG signature verification using app-crypt/gpgme

paludis

pbins	Enable binary package support. Adds dependency upon app-arch/libarchive
pink	Use a less boring colourscheme than the default
search-index	Enable cave search --index. Requires dev-db/sqlite.
xml	Build xml things for metadata.xml and GLSA support (needs dev-libs/libxml2).

pciutils

dns	Enable support for querying the central database of PCI IDs using DNS
kmod	Enable sys-apps/kmod support for the -k switch in lspci command
zlib	Support compressed pci.ids database

pcmciautils

staticsocket	Add support for static sockets

pcsc-lite

libusb	Use dev-libs/libusb detection to hotplug new smartcard readers. This flag should only be enabled if you're running a non-Linux kernel or you don't want to use sys-fs/udev.
policykit	Uses sys-auth/polkit to restrict access to smartcard readers or smartcars to given users.
udev	Use sys-fs/udev rules to handle devices' permissions and hotplug support. Unless you know what you're doing do not disable this flag on Linux kernels. This is provided as an option for completeness.

pcsc-tools

network-cron	Monthly cronjob the update-smartcard_list script

pkgcore

doc	Build and install API docs.

policycoreutils

audit	Enable support for sys-process/audit and use the audit_* functions (like audit_getuid instead of getuid())

portage

epydoc	Build html API documentation with epydoc.
ipc	Use inter-process communication between portage and running ebuilds.
native-extensions	Compiles native "C" extensions (speedups, instead of using python backup code). Currently includes libc-locales. This should only be temporarily disabled for some bootstrapping operations. Cross-compilation is not supported.
xattr	Preserve extended attributes (filesystem-stored metadata) when installing files. Usually only required for hardened systems.

proot

care	Build dynamic CARE binary (more info - http://reproducible.io/)

pyrenamer

music	Enable support for renaming music

qingy

consolekit	Enable native consolekit support
opensslcrypt	Encrypt communications between qingy and its GUI using dev-libs/openssl

razercfg

pm-utils	Installs the pm-utils hooks for suspend/resume and requires sys-power/pm-utils
qt4	Installs a qt UI. Requires dev-python/pyside

rng-tools

nistbeacon	Enable NIST beacon entropy support

roccat-tools

input_devices_roccat_ryosmkfx	Enable support for Ryos Mk FX keyboard.
input_devices_roccat_skeltr	Enable support for Skeltr keyboard.
input_devices_roccat_sova	Enable support for Sova keyboard.
input_devices_roccat_suora	Enable support for Suora keyboard.

s390-tools

fuse	build cmsfs-fuse to read files stored on a z/VM CMS disk
ncurses	build hyptop monitoring program
pfm	build the cpacfstats tool
zfcpdump	build the kernel disk dumping utility
zlib	build the zgetdump utility

selinux-python

audit	Enable support for sys-process/audit and use the audit_* functions (like audit_getuid instead of getuid())

smartmontools

caps	Build against sys-libs/libcap-ng to allow smartd to drop its privileges.
daemon	Install the monitoring daemon (smartd) and associated scripts.
minimal	Do not install the monitoring daemon and associated scripts.
update_drivedb	Install a script to update the drivedb file.

superiotool

pci	Support for PCI-attached "Super I/Os" (e.g. in VIA VT82686A/B).

systemd

apparmor	Enable AppArmor support
audit	Enable support for sys-process/audit
cryptsetup	Enable cryptsetup tools (includes unit generator for crypttab)
curl	Enable support for uploading journals
doc	Generate systemd.index.7 and systemd.directives.7
elfutils	Enable coredump stacktraces in the journal
gcrypt	Enable sealing of journal files using gcrypt
gnuefi	Enable EFI boot manager and stub loader (built using sys-boot/gnu-efi)
http	Enable embedded HTTP server in journald
importd	Enable import daemon
kmod	Enable kernel module loading via sys-apps/kmod
libidn2	If IDN support is enabled, use net-dns/libidn2 instead of net-dns/libidn
lz4	Enable lz4 compression for the journal
nat	Enable support for network address translation in networkd
qrcode	Enable qrcode output support in journal
sysv-utils	Install sysvinit compatibility symlinks and manpages for init, telinit, halt, poweroff, reboot, runlevel, and shutdown
usrmerge	Enable /usr merge (experimental)
vanilla	Disable Gentoo-specific behavior and compatibility quirks
xkb	Depend on x11-libs/libxkbcommon to allow logind to control the X11 keymap

tcp-wrappers

netgroups	Support matching NIS (host) netgroup names via the @netgroup syntax (if you don't know what this means, you most likely do not need it)

timer_entropyd

debug	Enable printf debugging and logging to the syslog at DEBUG level

tuxonice-userui

fbsplash	Add support for framebuffer splash

usb_modeswitch

jimtcl	Use dev-lang/jimtcl instead of dev-lang/tcl for smaller memory footprint

usermode-utilities

fuse	Build tools (currently umlmount) needing fuse

util-linux

caps	build setpriv helper (run programs with diff capabilities)
cramfs	build mkfs/fsck helpers for cramfs filesystems
fdformat	build fdformat (floppy disk format)
kill	build the kill program
pam	build runuser helper
suid	install mount/umount as setuid so non-root users may mount/umount devices, and wall/write as setgid so non-root users can notify other users
tty-helpers	install the mesg/wall/write tools for talking to local users

watchdog

nfs	enable support for checking nfs mounts

xinetd

rpc	support RPC services

sys-auth

consolekit

cgroups	Use the kernel to track processes instead of the session cookie.
evdev	For handling VT switching with a session controller.
pm-utils	Adds support for suspend/resume using sys-power/pm-utils
policykit	Use the PolicyKit framework (sys-auth/polkit) to get authorization for suspend/shutdown.
systemd-units	Install systemd unit files to replace the modern functionality of logind in sys-apps/systemd. Not recommended.

fingerprint-gui

upekbsapi	Add UPEK BSAPI drivers for identify functions on some readers

keystone

memcached	Installs dependencies needed for using memcached as a backend
mongo	Installs dependencies needed for using mongo as a backend

munge

gcrypt	Use libgcrypt instead of openssl

nss-mdns

search-domains	Honour search domains from /etc/resolv.conf (see bug #201948 for possible side effects)

nss-pam-ldapd

pynslcd	Install the python implementation along with the standard implementation
utils	Install the command-line utilities

oath-toolkit

pam	Build PAM module for pluggable login authentication for OATH
pskc	Build tools & library for the Portable Symmetric Key Container (PSKC) format per RFC6030

pam_mktemp

prevent-removal	If supported, set EXT2_APPEND_FL on /tmp/.private to prevent temporary directories from being removed

pam_mysql

openssl	Use OpenSSL for md5 and sha1 support

pam_u2f

debug	Enable debug messages using the pam logging macros. (Note: these will be visible on stdout for terminal logins).

pambase

consolekit	Enable pam_ck_connector module on local system logins. This allows for console logins to make use of ConsoleKit authorization.
cracklib	Enable pam_cracklib module on system authentication stack. This produces warnings when changing password to something easily crackable. It requires the same USE flag to be enabled on sys-libs/pam or system login might be impossible.
debug	Enable debug information logging on syslog(3) for all the modules supporting this in the system authentication and system login stacks.
elogind	Use pam_elogind module to register user sessions with elogind.
gnome-keyring	Enable pam_gnome_keyring module on system login stack. This enables proper Gnome Keyring access to logins, whether they are done with the login shell, a Desktop Manager or a remote login systems such as SSH.
minimal	Disables the standard PAM modules that provide extra information to users on login; this includes pam_tally (and pam_tally2 for Linux PAM 1.1 and later), pam_lastlog, pam_motd and other similar modules. This might not be a good idea on a multi-user system but could reduce slightly the overhead on single-user non-networked systems.
mktemp	Enable pam_mktemp module on system auth stack for session handling. This module creates a private temporary directory for the user, and sets TMP and TMPDIR accordingly.
nullok	Enable the nullok option with the pam_unix module. This allows people to login with blank passwords.
pam_krb5	Enable pam_krb5 module on system auth stack, as an alternative to pam_unix. If Kerberos authentication succeed, only pam_unix will be ignore, and all the other modules will proceed as usual, including Gnome Keyring and other session modules. It requires sys-libs/pam as PAM implementation.
pam_ssh	Enable pam_ssh module on system auth stack for authentication and session handling. This module will accept as password the passphrase of a private SSH key (one of ~/.ssh/id_rsa, ~/.ssh/id_dsa or ~/.ssh/identity), and will spawn an ssh-agent instance to cache the open key.
passwdqc	Enable pam_passwdqc module on system auth stack for password quality validation. This is an alternative to pam_cracklib producing warnings, rejecting or providing example passwords when changing your system password. It is used by default by OpenWall GNU/*/Linux and by FreeBSD.
securetty	Enable pam_securetty module in the login stack. Not generally relevant anymore as the login stack only refers to local logins and local terminals imply secure access in the first place.
sha512	Switch Linux-PAM's pam_unix module to use sha512 for passwords hashes rather than MD5. This option requires sys-libs/pam version 1.0.1 built against sys-libs/glibc version 2.7, if it's built against an earlier version, it will silently be ignored, and MD5 hashes will be used. All the passwords changed after this USE flag is enabled will be saved to the shadow file hashed using SHA512 function. The password previously saved will be left untouched. Please note that while SHA512-hashed passwords will still be recognised if the USE flag is removed, the shadow file will not be compatible with systems using an earlier glibc version.
systemd	Use pam_systemd module to register user sessions in the systemd control group hierarchy.

passwdqc

utils	Install pwqcheck and pwqgen helper utilities

polkit

elogind	Use sys-auth/elogind instead of sys-auth/consolekit for session tracking
systemd	Use sys-apps/systemd instead of sys-auth/consolekit for session tracking

sssd

acl	Build and use the cifsidmap plugin
augeas	Build internal configuration library
autofs	Build helper to let net-fs/autofs use sssd provided information
locator	Install sssd's Kerberos plugin
manpages	Build man pages with dev-libs/libxslt
netlink	Add support for netlink protocol via dev-libs/libnl
nfsv4	Add support for the nfsv4 idmapd plugin provided by net-libs/libnfsidmap
ssh	Build helper to let net-misc/openssh use sssd provided information
sudo	Build helper to let app-admin/sudo use sssd provided information

ykpers

consolekit	Use sys-auth/consolekit and virtual/udev to allow access to the YubiKey HID device to the console user.

sys-block

f3

extra	Build the additional f3probe, f3brew and f3fix utility (requires sys-block/parted and virtual/udev)

fio

aio	Enable AIO ioengine
glusterfs	Enable GlusterFS gfapi support via sys-cluster/glusterfs
gnuplot	Install tools for generating gnuplots
numa	Enable numa support
rbd	Enable Rados block device support via sys-cluster/ceph
rdma	Enable infiniband support via sys-fabric/librdmacm

gparted

btrfs	Include Btrfs support (sys-fs/btrfs-progs)
cryptsetup	Include LUKS volume support (sys-fs/cryptsetup)
dmraid	Support for dmraid devices, also known as ATA-RAID, or Fake RAID.
f2fs	Include F2FS support (sys-fs/f2fs-tools)
fat	Include FAT16/FAT32 support (sys-fs/dosfstools)
hfs	Include HFS support (sys-fs/hfsutils)
jfs	Include JFS support (sys-fs/jfsutils)
mdadm	Support for Linux software RAID.
ntfs	Include NTFS support (sys-fs/ntfs3g)
reiser4	Include ReiserFS4 support (sys-fs/reiser4progs)
reiserfs	Include ReiserFS support (sys-fs/reiserfsprogs)
udf	Include UDF support (sys-fs/udftools)
xfs	Include XFS support (sys-fs/xfsprogs, sys-fs/xfsdump)

open-iscsi

rdma	Support iSCSI over RDMA
tcp	Support iSCSI over TCP

parted

debug	Enable debugging as encouraged by upstream: [The default configuration] includes --enable-debug (by default), which contains many assertions. Obviously, these "waste" space, but in the past, they have caught potentially dangerous bugs before they would have done damage, so we think it's worth it. Also, it means we get more bug reports ;)
device-mapper	Enable device-mapper support from sys-fs/lvm2 in parted

partimage

nologin	Do not include login support when connecting partimaged

perccli

efi	Install EFI variant as well

sas2ircu

efi	Install EFI variant as well

sas3flash

efi	Install EFI variant as well

sas3ircu

efi	Install EFI variant as well

tgt

fcoe	Add support for FCoE protocol
fcp	Add support for new FC protocol
ibmvio	Add support for IBM Virtual I/O
rbd	Add support for ceph block devices

sys-boot

grub

device-mapper	Enable support for device-mapper from sys-fs/lvm2
efiemu	Build and install the efiemu runtimes
fonts	Build and install fonts for the gfxterm module
libzfs	Enable support for sys-fs/zfs
mount	Build and install the grub-mount utility
multislot	Allow concurrent installation of sys-boot/grub SLOT 0 and sys-boot/grub SLOT 2 by renaming all programs.
themes	Build and install GRUB themes (starfield)
truetype	Build and install grub-mkfont conversion utility

lilo

device-mapper	Enable support for device-mapper from sys-fs/lvm2
minimal	Do not install the dolilo helper script
pxeserial	Avoid character echo on PXE serial console

plymouth

gdm	Enables smooth transition to GDM
libkms	Provides abstraction to the DRM drivers (intel, nouveau and vmwgfx at this moment)
pango	Adds support for printing text on splash screen and text prompts, e.g. for password

refind

btrfs	Builds the EFI binary btrfs filesystem driver
ext2	Builds the EFI binary ext2 filesystem driver
ext4	Builds the EFI binary ext4 filesystem driver
gnuefi	Compile using GNU-EFI instead of Tianocore
hfs	Builds the EFI binary hfs filesystem driver
iso9660	Builds the EFI binary iso9660 filesystem driver
ntfs	Builds the EFI binary ntfs filesystem driver
reiserfs	Builds the EFI binary reiserfs filesystem driver

sys-cluster

ceph

babeltrace	Add support for LTTng babeltrace
cephfs	Build support for cephfs, a POSIX compatible filesystem built on top of ceph
cryptopp	Use dev-libs/crypto++ for cryptography
fuse	Build fuse client
jemalloc	Use dev-libs/jemalloc for allocations
libaio	Use libaio as asynchronous input/output library
libatomic	Use libatomic instead of builtin atomic operations
lttng	Add support for LTTng
mgr	Build the ceph-mgr daemon
nss	Use dev-libs/nss for cryptography
radosgw	Add radosgw support
xfs	Add xfs support
zfs	Add zfs support

charm

ampi	Build implementation of MPI on top of Charm++
charmdebug	Enable the charm debugger
charmproduction	Optimize performance of Charm++ runtime
charmtracing	Enable tracing support in Charm++
cmkopt	Enable CMK optimisation
mlogft	Compile with Charm++ message logging fault tolerance support
numa	Support memory affinity with NUMA
syncft	Compile with Charm++ fault tolerance support
tcp	Use TCP (instead of UPD) for socket communication

cinder

api	Installs the initscripts for the cinder api service
iscsi	Allow using an iSCSI remote storage server as pool for disk image storage
lvm	Allow using the Logical Volume Manager (sys-fs/lvm2) as pool for disk image storage
memcached	Installs the memcached server
rdma	Enable rdma storage backend support
scheduler	Installs the initscripts for the cinder scheduler service
tcp	Enables tcp support for the iscsi backend
tgt	Enable tgt storage backend support
volume	Installs the initscripts for the cinder volume service

cluster-glue

libnet	Force use of net-libs/libnet

corosync

infiniband	Enable Infiniband RDMA transport support

drbd

heartbeat	Enable Heartbeat integration
pacemaker	Enable Pacemaker integration
xen	Enable Xen integration

drbd-utils

heartbeat	Enable Heartbeat integration
pacemaker	Enable Pacemaker integration
xen	Enable Xen integration

galera

garbd	Install Galera Arbitrator - a stateless daemon which acts as a lightweight group member

gearmand

memcache	Support memcache daemon (via dev-libs/libmemcached) for the queue storage.
tokyocabinet	Support dev-db/tokyocabinet for the queue storage.

glusterfs

bd-xlator	Enable the blockdevice translator (requires sys-fs/lvm2)
crypt-xlator	Enable the encryption translator
fuse	Add FUSE mount helper
georeplication	Enable support for georeplication (requires dev-lang/python)
glupy	Enable support for translators written in Python
infiniband	Add support for Infiniband ibverbs transport. Libraries can be found in science overlay
libtirpc	Build against net-libs/libtirpc for RPC support
qemu-block	Transparently create files as QCow2/QED images in the backend, including the possibility to snapshot.
rsyslog	Install configuration snippet for app-admin/rsyslog
systemtap	Enable support for dev-util/systemtap
tiering	Enable support for data classification/tiering (requires dev-db/sqlite SLOT 3)

heat

memcached	Installs the memcached server

hpx

jemalloc	Use dev-libs/jemalloc for memory allocation
papi	Use dev-libs/papi for NaCl
perftools	Use dev-util/google-perftools for memory allocation
tbb	Use dev-cpp/tbb for memory allocation

legion

gasnet	Enable GASNet lib support
hwloc	Enable HWLoc lib support

maui

pbs	Enable pbs integration
slurm	Enable slurm integration

moosefs

cgi	Install CGI server and scripts.
fuse	Install the mfsmount utility.

mpich

mpi-threads	Enable MPI_THREAD_MULTIPLE
romio	Build the ROMIO MPI-IO component

mpich2

mpi-threads	Enable MPI_THREAD_MULTIPLE
romio	Enable romio, a high-performance portable MPI-IO implementation

mvapich2

large-cluster	Automatically generated description for large-cluster
medium-cluster	Automatically generated description for medium-cluster
romio	Automatically generated description for romio

neutron

compute-only	Only install things needed on compute hosts
dhcp	Installs the initscripts for the neutron dhcp service
l3	Installs the initscripts for the neutron l3 agent service
linuxbridge	Installs the initscripts for the neutron linuxbridge agent service
metadata	Installs the initscripts for the neutron metadata agent service
openvswitch	Installs the initscripts for the neutron openvswitch agent service
server	Installs the initscripts for the neutron server service

nova

compute	Installs the initscripts for the nova volume service
compute-only	only install stuff needed for a compute host
iscsi	Installs iscsi helper udev scripts
memcached	Installs the memcached server
novncproxy	Installs the initscripts for the nova novncproxy service
openvswitch	Installs openvswitch for the neutron openvswitch support
rabbitmq	Installs the rabbitmq server

ocfs

aio	Add aio support

openmpi

cma	Enable the CMA (Cross Memory Attach) MCA
cuda	Add GPU direct support
heterogeneous	Enable features required for heterogeneous platform support
mpi-threads	Enable MPI_THREAD_MULTIPLE
numa	Enable numactl to allow binding processes to CPUs
pbs	Add support for the Portable Batch System (PBS)
romio	Build the ROMIO MPI-IO component
vt	Enable bundled VampirTrace support

openstack-meta

cinder	Installs Openstack Cinder
glance	Installs Openstack Glance
heat	Installs Openstack Heat
keystone	Installs Openstack Keystone
neutron	Installs Openstack Neutron
nova	Installs Openstack Nova
swift	Installs Openstack Swift

pacemaker

cman	Enable sys-cluster/cman support.
heartbeat	Enable sys-cluster/heartbeat support.
smtp	Enable SMTP support via net-libs/libesmtp

resource-agents

libnet	Force use of net-libs/libnet
rgmanager	Install resources for sys-cluster/rgmanager

singularity

slurm	Compile spank plugin for sys-cluster/slurm

slurm

multiple-slurmd	Allow multiple slurmd to run
munge	Enable authentication via munge
torque	Enable perl scripts that emulates pbs (qstat, qsub etc.)

swift

account	adds swift account support
container	adds swift container support
memcached	adds memcached support
object	adds swift object support
proxy	adds swift proxy support

torque

autorun	Enable the AUTORUN_JOBS codebase
cgroups	Enable pbs_mom to use linux cgroups to isolate jobs
cpusets	Enable pbs_mom to utilize linux cpusets if available
drmaa	Enable the Distributed Resource Management Application API
munge	Enable authentication via munge
nvidia	Enable management of Nvidia GPUs
quickcommit	Enable the QUICKCOMMIT codebase
server	Enable compilation of pbs_server and pbs_sched

vzctl

ploop	Add support for ploop devices via sys-cluster/ploop
vzmigrate	Add support for container migration

sys-devel

autogen

libopts	install the libopts tarball (a few packages want this for developing)

binutils

multitarget	Adds support to binutils for cross compiling (does not work with gas)

binutils-apple

classic	Use nm, otool, etc. from this ebuild instead of llvm-based tools
libcxx	Add support for libcxx
lto	Add support for Link-Time Optimization with LLVM
multitarget	Compile for non-standard target architectures (ppc and ppc64) -- experimental, Gentoo only
tapi	Build against sys-libs/tapi

binutils-hppa64

multitarget	Adds support to binutils for cross compiling (does not work with gas)

clang

default-compiler-rt	Use compiler-rt instead of libgcc as the default rtlib for clang
default-libcxx	Use libc++ instead of libstdc++ as the default stdlib for clang
multitarget	Build all host targets (default: host only)
static-analyzer	Install the Clang static analyzer
z3	Enable the static analyzer constraint manager backend using sci-mathematics/z3

clang-runtime

compiler-rt	Install sys-libs/compiler-rt for -rtlib=compiler-rt
libcxx	Install sys-libs/libcxx for -stdlib=libc++
openmp	Install sys-libs/libomp for -fopenmp support
sanitize	Enable compiler-rt sanitizer (-fsanitize*) support

distcc

crossdev	Enable support for sys-devel/crossdev
gssapi	Enable support for net-libs/libgssglue

gcc

awt	Useful only when building GCJ, this enables Abstract Window Toolkit (AWT) peer support on top of GTK+
cilk	Support the Cilk Plus language (C/C++ based languages for parallel programming)
d	Enable support for the D programming language
fixed-point	Enable fixed-point arithmetic support for MIPS targets in gcc (Warning: significantly increases compile time!)
go	Build the GCC Go language frontend.
graphite	Add support for the framework for loop optimizations based on a polyhedral intermediate representation
jit	Enable libgccjit so other applications can embed gcc for Just-In-Time compilation. This will slow down the compiler a bit as it forces all of the toolchain to be shared libs.
libssp	Build SSP support into a dedicated library rather than use the code in the C library (DO NOT ENABLE THIS IF YOU DON'T KNOW WHAT IT DOES)
mpx	Enable support for Intel Memory Protection Extensions (MPX)
mudflap	Add support for mudflap, a pointer use checking library
nopie	Disable PIE support (NOT FOR GENERAL USE)
nossp	Disable SSP support (NOT FOR GENERAL USE)
objc	Build support for the Objective C code language
objc++	Build support for the Objective C++ language
objc-gc	Build support for the Objective C code language Garbage Collector
pgo	Build GCC using Profile Guided Optimization (PGO)
regression-test	Run the testsuite and install the results (requires FEATURES=test)
sanitize	Build support for various sanitizer functions (ASAN/TSAN/etc...)
ssp	Build packages with stack smashing protector on by default
vtv	Build support for virtual table verification (a C++ hardening feature)

gcc-apple

objc	Build support for the Objective C code language
objc++	Build support for the Objective C++ language
regression-test	Run the testsuite and install the results (requires FEATURES=test)

gdb

client	Install the main "gdb" program (most people want this)
lzma	Support lzma compression in ELF debug info
multitarget	Support all known targets in one gdb binary
python	Enable support for the new internal scripting language, as well as extended pretty printers
server	Install the "gdbserver" program (useful for embedded/remote targets)
xml	Support parsing XML data files needed (at least) for cpu features, memory maps, and syscall tracing

gettext

cvs	When running `autopoint`, use cvs to store the internal development files; this requires cvs at runtime, but will be faster/smaller than raw archives
git	When running `autopoint`, use git to store the internal development files; this requires git at runtime, but will be faster/smaller than raw archives

kgcc64

regression-test	Run the testsuite and install the results (requires FEATURES=test)

llvm

clang	Build the clang C/C++ compiler
default-compiler-rt	Use compiler-rt instead of libgcc as the default rtlib for clang
default-libcxx	Use libc++ instead of libstdc++ as the default stdlib for clang
doc	Build and install the HTML documentation and regenerate the man pages
gold	Build the gold linker plugin
lldb	Build the lldb debugger
multitarget	Build all host targets (default: host only)
ncurses	Support querying terminal properties using ncurses' terminfo
sanitize	Build compiler-rt's sanitizers
static-analyzer	Install the Clang static analyzer (requires USE=clang)

sparse

gtk	Build the test-inspect utility (requires x11-libs/gtk+ version 2)
llvm	Build the sparse-llvm utility
xml	Build the c2xml utility (requires dev-libs/libxml2)

sys-fabric

ofed

dapl	Add support for DAPL abstraction layer
diags	Add dignostic tools for infiniband
ibacm	Add support for userspace pre-connection services
mstflint	Tools to burn Mellanox firmware
opensm	Add OpenSM - Subnet manager for infiniband
perftest	Add perftest utils
qperf	Add rdma tests
rds	Tools to manage rds sockets
srp	Suport for userspace part for srp initiator

opensm

tools	Install ssld extra tool

sys-firmware

edk2-ovmf

binary	Use pre-built binaries

intel-microcode

initramfs	install a small initramfs for use with CONFIG_MICROCODE_EARLY
monolithic	install the large text microcode.dat (used by older kernels via microcode_ctl)
split-ucode	install the split binary ucode files (used by the kernel directly)

ipxe

efi	Build an EFI program for using PXE
iso	Build a bootable ISO for using PXE
lkrn	Build a linux kernel bootable file for using with grub/etc...
qemu	Build the required PXE ROM images for app-emulation/qemu
undi	Build a Universal Network Device Interface driver chainloading your existing PXE NIC into iPXE
usb	Build a bootable USB image for using PXE
vmware	Build the PXE ROM images that VMWare uses

seabios

binary	Use official upstream pre-built binaries
seavgabios	Include SeaVGABIOS binaries (replacement for vgabios)

sigrok-firmware-fx2lafw

binary	Use official upstream pre-built binaries

vgabios

binary	Use official upstream pre-built binaries (only default and cirrus images)

sys-freebsd

boot0

tftp	Enable PXE/TFTP boot support.
zfs	Enable booting on ZFS filesystems.

freebsd-lib

hesiod	Enable support for net-dns/hesiod
netware	Build libraries and tools to work with NetWare protocols (IPX and NCP).
zfs	Enable ZFS support.

freebsd-rescue

netware	Build tools to work with NetWare protocols (IPX and NCP).
zfs	Enable ZFS support.

freebsd-sbin

ipfilter	Build tools to administer the ipfilter firewall.
netware	Build libraries and tools to work with NetWare protocols (IPX and NCP).
pf	Build tools to administer the PF firewall.
zfs	Enable ZFS support.

freebsd-share

isdn	Enable ISDN support
zfs	Enable ZFS support.

freebsd-sources

build-kernel	Build and install a kernel (recommended).
dtrace	Enable DTrace support.
zfs	Enable ZFS support.

freebsd-ubin

ar	Build FreeBSD's ar and ranlib replacements based on libarchive. The toolchain will still use binutils' version but you can play with it. They have been renamed to freebsd-ar and freebsd-ranlib not to collide with binutils.
audit	Build auditing tools
netware	Build libraries and tools to work with NetWare protocols (IPX and NCP)
zfs	Enable ZFS support (for fstat actually).

freebsd-usbin

audit	Build auditing tools.
floppy	Enable floppy disk utilities (fdcontrol, fdformat, fdread, fdwrite).
netware	Build libraries and tools to work with NetWare protocols (IPX and NCP).
zfs	Enable ZFS support.

sys-fs

aufs3

debug	Enable additional debugging support
fuse	Enable fuse support
hfs	Enable hfs support
inotify	Enable inotify support
kernel-patch	Patch the current kernel for aufs3 support
nfs	Enable support for nfs export
pax_kernel	Apply patch needed for pax enabled kernels
ramfs	Enable initramfs/rootfs support

aufs4

debug	Enable additional debugging support
fuse	Enable fuse support
hfs	Enable hfs support
inotify	Enable inotify support
kernel-patch	Patch the current kernel for aufs3 support
nfs	Enable support for nfs export
pax_kernel	Apply patch needed for pax enabled kernels
ramfs	Enable initramfs/rootfs support

btrfs-progs

convert	Build ext2 conversion utility (btrfs-convert)
reiserfs	Enable reiserfs support in btrfs-convert tool.
static	Build static binaries in addition to the dynamic ones
zstd	Enable zstd compression support.

cryfs

update-check	Enable automatic checking for updates and security vulnerabilities

cryptsetup

argon2	Enable password hashing algorithm from app-crypt/argon2
gcrypt	Use dev-libs/libgcrypt crypto backend
kernel	Use kernel crypto backend (mainly for embedded systems)
nettle	Use dev-libs/nettle crypto backend
openssl	Use dev-libs/openssl crypto backend
pwquality	Use dev-libs/libpwquality for password quality checking
reencrypt	Build cryptsetup-reencrypt
urandom	Use /dev/urandom instead of /dev/random

dmraid

dietlibc	Compile against dev-libs/dietlibc
intel_led	Enable Intel LED support
klibc	Compile against dev-libs/klibc
led	Enable LED support
mini	Create a minimal binary suitable for early boot environments

dosfstools

compat	Install symlinks for legacy names of the tools

e2fsprogs

fuse	Build fuse2fs, a FUSE file system client for ext2/ext3/ext4 file systems

ecryptfs-utils

gpg	Enable app-crypt/gnupg key module
openssl	Enable dev-libs/openssl key module
pkcs11	Enable PKCS#11 (Smartcards) key module
tpm	Enable support for Trusted Platform Module (TPM) using app-crypt/trousers

eudev

blkid	enable blkid support
efi	enable EFI support
hwdb	read vendor/device string database and add it to udev database
kmod	enable module loading through libkmod
rule-generator	install legacy rule generator rules and support scripts - note that the functionality within was dropped from sys-fs/udev as it is not stable in all cases; use at your own risk
smack	enable SMACK security model

ext4magic

expert-mode	Builds ext4magic with expert mode. Highly useful in recovering data from a corrupted filesystem
file-attr	Enable the recovery of file attributes (append, immutable, nodump etc)

lessfs

filelog	Enable the ability to log to a file instead of syslog
memtrace	Enable leefs to create a report regarding the memory allocation. This feature should be used for debugging purposes to avoid performance degradation
snappy	Enable snappy compression using the app-arch/snappy library

loop-aes

cpu_flags_x86_padlock	Use VIA padlock instructions, detected at run time, code still works on non-padlock processors
extra-ciphers	Enable extra ciphers
keyscrub	Protects the encryption key in memory but takes more cpu resources

lvm2

clvm	Allow users to build clustered lvm2
cman	Cman support for clustered lvm
corosync	Corosync support for clustered lvm
device-mapper-only	Build only device-mapper and not the rest of LVM2 (UNSUPPORTED)
lvm1	Allow users to build lvm2 with lvm1 support
lvm2create_initrd	Install lvm2create_initrd script and pull in sys-apps/makedev for the /sbin/MAKEDEV command
openais	Openais support for clustered lvm
sanlock	Enable lvmlockd with support for sanlock
thin	Support for thin volumes

mtpfs

mad	Enable handling of MP3's metadata

multipath-tools

rbd	Enable Rados block device support via sys-cluster/ceph

ntfs3g

external-fuse	Use external FUSE library instead of internal one. Must be disabled for unprivileged mounting to work.
ntfsdecrypt	Build and install the ntfsdecrypt application.
ntfsprogs	Include internal version of ntfsprogs.

ocfs2-tools

external	Enable external locking

owfs

ftdi	Enable support for USB FTDI chips via dev-embedded/libftdi
ftpd	Enable building the OWFS FTP server (owftpd)
fuse	Enable building the FUSE-based OWFS client (owfs)
httpd	Enable building the OWFS web server (owhttpd)
parport	Enable support for the DS1410E parallel port adapter
zeroconf	Enables support for zero-configuration networking via net-dns/avahi

quota

netlink	Compile daemon receiving quota messages via netlink
rpc	Enable quota interaction via RPC

squashfs-tools

lz4	Enable support for LZ4 compression using app-arch/lz4
xz	Enable support for XZ ("LZMA2") compression using app-arch/xz-utils
zstd	Enable support for ZSTD compression using app-arch/zstd

squashfuse

lz4	Enable support for lz4 compression

udev

firmware-loader	Enable the userspace firmware loader (DEPRECATED, replaced by the in-kernel loader starting from 3.8)
gudev	Build the gobject interface library
kmod	Enable kernel module loading/unloading support using sys-apps/kmod

udisks

cryptsetup	Enable sys-fs/cryptsetup support
elogind	Use sys-auth/elogind for session tracking
gptfdisk	Pull in sys-apps/gptfdisk for sgdisk command as used by partitioning functionality
lvm	Add support for Logical Volume Management via sys-fs/lvm2.
remote-access	Control whether connections from other clients over LAN are allowed
systemd	Support sys-apps/systemd's logind

zfs

kernel-builtin	Disable dependency on sys-fs/zfs-kmod under the assumption that ZFS is part of the kernel source tree
rootfs	Enable dependencies required for booting off a pool containing a rootfs
test-suite	Install regression test suite

zfs-kmod

rootfs	Install zfs-shutdown script to support exporting a pool containing rootfs

sys-kernel

aufs-sources

experimental	Apply experimental patches; for more information, see "https://wiki.gentoo.org/wiki/Project:Kernel/Experimental".
module	Patch kernel to allow aufs being build as a module.
vanilla	Use vanilla kernel sources without applying genpatches. WARNING: This flag will drop all support from the Gentoo Kernel Security team

ck-sources

deblob	Remove binary blobs from kernel sources to provide libre license compliance.
experimental	Apply experimental patches; for more information, see "https://wiki.gentoo.org/wiki/Project:Kernel/Experimental".

dracut

debug	Module installing additional tools like strace, file editor, ssh and more

genkernel

cryptsetup	Enable support for Luks disk encryption using sys-fs/cryptsetup
firmware	Prefer system firmware sys-kernel/linux-firmware over local copy.

genkernel-next

cryptsetup	Enable support for Luks disk enrcyption using sys-fs/cryptsetup
dmraid	Enable support for DMRAID (include dmraid dependency)
gpg	Enable support for GPG (include gnupg dependency)
iscsi	Enable support for open-iscsi (include open-iscsi dependency)
mdadm	Enable support for mdadm (include mdadm dependency)
plymouth	Enable support for Plymouth (include Plymouth dependency)

gentoo-sources

experimental	Apply experimental patches; for more information, see "https://wiki.gentoo.org/wiki/Project:Kernel/Experimental".

hardened-sources

deblob	Remove binary blobs from kernel sources to provide libre license compliance.

linux-docs

html	Install HTML documentation

linux-firmware

savedconfig	Allows individual selection of firmware files

mips-sources

experimental	Apply experimental (80xx) patches.
ip27	Enables additional support for SGI Origin (IP27)
ip28	Enables additional support for SGI Indigo2 Impact R10000 (IP28)
ip30	Enables support for SGI Octane (IP30, 'Speedracer')

rt-sources

deblob	Remove binary blobs from kernel sources to provide libre license compliance.

tuxonice-sources

experimental	Apply experimental patches; for more information, see "https://wiki.gentoo.org/wiki/Project:Kernel/Experimental".

sys-libs

binutils-libs

64-bit-bfd	Support 64-bit targets even on 32-bit hosts (is ignored on 64-bit hosts)
multitarget	Enable all possible targets in libbfd

compiler-rt

clang	Force building using installed clang (rather than the default CC/CXX).

db

rpc	Enable rpc client/server

freeipmi

nagios	Install a nagios plugin to check sensors' status.

gdbm

berkdb	enable compatibility layer for UNIX-like dbm and ndbm interfaces
exporter	enable gdbmexport binary for exporting data from gdbm-1.8 databases into gdbm-1.9

glibc

compile-locales	build *all* locales in src_install; this is generally meant for stage building only as it ignores /etc/locale.gen file and can be pretty slow
debug	When USE=hardened, allow fortify/stack violations to dump core (SIGABRT) and not kill self (SIGKILL)
gd	build memusage and memusagestat tools
nscd	Build, and enable support for, the Name Service Cache Daemon
rpc	Enable obsolete RPC/NIS layers
suid	Make internal pt_chown helper setuid -- not needed if using Linux and have /dev/pts mounted with gid=5
systemtap	enable systemtap static probe points

gwenhywfar

fox	Use x11-libs/fox graphical toolkit

libblockdev

bcache	Enable block device cache support.
cryptsetup	Enable sys-fs/cryptsetup support
dmraid	Support for dmraid devices, also known as ATA-RAID, or Fake RAID.
kbd	Enable kernel block device support.
lvm	Enable support for Logical Volume Management via sys-fs/lvm2.

libcxx

libcxxabi	Build on top of sys-libs/libcxxabi instead of gcc's libsupc++ (avoids depending on gcc).
libcxxrt	Build on top of sys-libs/libcxxrt instead of gcc's libsupc++ (avoids depending on gcc).
libunwind	Use libunwind instead of libgcc_s for stack unwinding, thus avoiding dependence on gcc.

libcxxabi

libunwind	Use libunwind instead of libgcc_s for stack unwinding, thus avoiding dependency on gcc

libcxxrt

libunwind	Use libunwind instead of libgcc_s for unwinding. This should allow avoiding relying on sys-devel/gcc but for now clang is setup to use libgcc_s.

libhugetlbfs

perl	Install the cpupcstat tool and some perl modules

libomp

hwloc	Enable CPU affinity support via hwloc
ompt	Enable OpenMP Tools Interface support

libselinux

pcre2	Use dev-libs/libpcre2 for fcontext regexes

libunwind

debug-frame	Adds support for DWARF .debug_frame section: Use the information from this section if available
libatomic	Use libatomic instead of builtin atomic operations

musl-nscd

minimal	Only installs the header files

ncurses

ada	Add bindings for the ADA programming language
tinfo	Build curses library (libncurses) sep from the low-level terminfo library (libtinfo) -- usually needed only for binary packages -- but it is binary compatible in either mode
trace	Enable test trace() support in ncurses calls

pam

berkdb	Build the pam_userdb module, that allows to authenticate users against a Berkeley DB file. Please note that enabling this USE flag will create a PAM module that links to the Berkeley DB (as provided by sys-libs/db) installed in /usr/lib and will thus not work for boot-critical services authentication.
cracklib	Build the pam_cracklib module, that allows to verify the chosen passwords' strength through the use of sys-libs/cracklib. Please note that simply enabling the USE flag on this package will not make use of pam_cracklib by default, you should also enable it in sys-auth/pambase as well as update your configuration files.

readline

utils	Install rlfe (ReadLine Front-End) helper tool -- a wrapper program for making any stdin use readline

talloc

compat	Enable extra compatibility stuff

timezone-data

leaps_timezone	Install the set of "right" timezones; these timezones include leap seconds when counting seconds since the epoch (while POSIX does not) as they are based on the TAI (International Atomic Time) clock

uclibc

rpc	Enable sun nis/rpc support (you should use libtirpc though)
savedconfig	Adds support for user defined configs
ssp	Force the use of ssp to be built into a hardened uclibc setup
uclibc-compat	Build uclibc with backwards compatible options
wordexp	Add support for word expansion (wordexp.h)

uclibc-ng

rpc	Enable sun nis/rpc support (you should use libtirpc though)
symlink-compat	Explicitly add sym links for libdl.so.0, libm.so.0, and friends for backward compatibility with sys-libs/uclibc-ng-1.0.17 and earlier

zlib

minizip	include the minizip library for quick and dirty zip extraction

sys-power

apcupsd

modbus	Enable MODBUS support over USB

cpupower

cpufreq_bench	Build and install the cpufreq_bench binary

nut

ipmi	Support IPMI-based UPSes.
ups_drivers_al175	Driver for Eltek UPS models with AL175 alarm module
ups_drivers_apcsmart	Driver for American Power Conversion Smart Protocol UPS equipment
ups_drivers_apcsmart-old	Driver for American Power Conversion Smart Protocol UPS equipment
ups_drivers_apcupsd-ups	Driver for apcupsd client access
ups_drivers_bcmxcp	Driver for UPSes supporting the serial BCM/XCP protocol
ups_drivers_bcmxcp_usb	Experimental driver for UPSes supporting the BCM/XCP protocol over USB
ups_drivers_belkin	Driver for Belkin serial UPS equipment
ups_drivers_belkinunv	Driver for Belkin "Universal UPS" and compatible
ups_drivers_bestfcom	Driver for Best Power Fortress/Ferrups
ups_drivers_bestfortress	Driver for old Best Fortress UPS equipment
ups_drivers_bestuferrups	Driver for Best Power Micro-Ferrups
ups_drivers_bestups	Driver for Best Power / SOLA (Phoenixtec protocol) UPS equipment
ups_drivers_blazer_ser	Driver for Megatec/Q1 protocol serial based UPS equipment
ups_drivers_blazer_usb	Driver for Megatec/Q1 protocol USB based UPS equipment
ups_drivers_clone	Fake driver to clone outlets for device grouping
ups_drivers_clone-outlet	Fake driver to clone outlets for device grouping
ups_drivers_dummy-ups	Driver for multi-purpose UPS emulation
ups_drivers_etapro	Driver for ETA UPS equipment
ups_drivers_everups	Driver for Ever UPS models
ups_drivers_gamatronic	Driver for Gamatronic UPS equipment
ups_drivers_genericups	Driver for contact-closure UPS equipment
ups_drivers_isbmex	Driver for ISBMEX UPS equipment
ups_drivers_ivtscd	driver for the IVT Solar Controller Device
ups_drivers_liebert	Driver for Liebert contact-closure UPS equipment
ups_drivers_liebert-esp2	Driver for Liebert UPS, using the ESP-II serial protocol
ups_drivers_masterguard	Driver for Masterguard UPS equipment
ups_drivers_metasys	Driver for Meta System UPS equipment
ups_drivers_mge-shut	Driver for SHUT Protocol UPS equipment
ups_drivers_mge-utalk	Driver for MGE UPS SYSTEMS UTalk protocol equipment
ups_drivers_microdowell	Driver for Microdowell Enterprise UPS series
ups_drivers_netxml-ups	Driver for Eaton / MGE Network Management Card / Proxy (XML/HTTP Protocol) equipment
ups_drivers_nut-ipmipsu	Driver for IPMI Power Supply Units (PSU)
ups_drivers_nutdrv_qx	Driver for Q* protocol serial and USB based UPS equipment
ups_drivers_oldmge-shut	Driver for SHUT Protocol UPS equipment (older implementation)
ups_drivers_oneac	Driver for Oneac UPS equipment
ups_drivers_optiups	Driver for Opti-UPS (Viewsonic) UPS and Zinto D (ONLINE-USV) equipment
ups_drivers_powercom	UPS driver for serial Powercom/Trust/Advice UPS equipment
ups_drivers_powerpanel	Driver for PowerPanel Plus compatible UPS equipment
ups_drivers_rhino	Driver for Brazilian Microsol RHINO UPS equipment
ups_drivers_richcomm_usb	Driver UPS equipment using Richcomm dry-contact to USB solution
ups_drivers_riello_ser	Driver for Riello UPS Protocol UPS equipment
ups_drivers_riello_usb	Driver for Riello UPS Protocol UPS equipment via USB
ups_drivers_safenet	Driver for SafeNet compatible UPS equipment
ups_drivers_snmp-ups	Multi-MIB Driver for SNMP UPS equipment
ups_drivers_solis	Driver for Brazilian Microsol SOLIS UPS equipment
ups_drivers_tripplite	Driver for Tripp-Lite SmartPro UPS equipment
ups_drivers_tripplite_usb	Driver for older Tripp Lite USB UPSes (not PDC HID)
ups_drivers_tripplitesu	Driver for Tripp-Lite SmartOnline (SU) UPS equipment
ups_drivers_upscode2	Driver for UPScode II compatible UPS equipment
ups_drivers_usbhid-ups	Driver for USB/HID UPS equipment
ups_drivers_victronups	Driver for IMV/Victron UPS unit Match, Match Lite, NetUps

nvclock

gtk	Install the GTK+ based graphical interface
nvcontrol	Add NVCONTROL support for OpenGL options

phctool

sudo	Enable support for sudo to run gui from non-root user

pm-utils

ntp	Install support for net-misc/ntp

powermgmt-base

pm-utils	Adds support for on_ac_power through sys-power/pm-utils

sispmctl

gemplug	Install gemplug (management script)

suspend

crypt	Allows suspend and resume from encrypted disk
fbsplash	Add support for framebuffer splash

sys-process

audit

gssapi	Enable GSSAPI support

criu

setproctitle	Make process titles of service workers to be more verbose

cronie

anacron	Install the periodic anacron command scheduler.
inotify	Enable inotify filesystem monitoring support.

fcron

debug	Enable debug code and output. Since version 3.0.5 this will no longer force foreground execution, and fcron will be able to run as a service properly.
mta	Enable mta support for sending emails from fcron
pam	Enable PAM support for fcron. This means that fcron will pass through the "fcron" stack before executing the jobs, and fcrontab will use the "fcrontab" stack to authenticate the user before editing its crontab file.
system-crontab	Set up fcron to respect /etc/crontab and /etc/cron.d. If this flag is disabled, /etc/cron.d and /etc/crontab will be ignored, but /etc/cron.{hourly,daily,weekly,monthly} will still be respected.

htop

oom	Add column to track the OOM-killer score of processes
openvz	Enable openvz support
vserver	Enable vserver support

lsof

rpc	support looking up RPC service info

procps

elogind	Use sys-auth/elogind for session tracking.
kill	Build the kill program
modern-top	Enables new startup defaults of top. Keeps old defaults if disabled
ncurses	Build programs that use ncurses: top, slabtop, watch

systemd-cron

cron-boot	Include support for the boot timer.
etc-crontab-systemd	Use dedicated /etc/crontab-systemd instead of parsing /etc/crontab
minutely	Support /etc/cron.minutely
setgid	Compile setgid C helper for crontab. Needs GCC or Clang.
yearly	Support /etc/cron.yearly

tini

args	Enable argument parsing.

virtual

ffmpeg

opus	Use the external opus library for encoding and decoding.

linux-sources

firmware	Install linux kernel firmware

mpi

romio	Enable romio, a high-performance portable MPI-IO

mysql

embedded	Build embedded server (libmysqld)
server	Build server (mysqld)

podofo-build

boost	Add support for boost
tools	Build and install commandline tools.

ssh

minimal	Prefer net-misc/dropbear over net-misc/openssh

wine

d3d9	Enable Ixit's Gallium Nine Patchset
staging	Enable Wine-Staging's Patchset

www-apache

mod_backtrace

unwind	Use sys-libs/libunwind to provide better resolution of function names.

mod_extract_forwarded

mod_proxy	Enable support for Apache's internal proxy

mod_musicindex

archive	Add archive support
cache	Add File cache support
mysql	Add MySQL cache support

mod_nss

ecc	enable Elliptical Curve Cyptography

mod_perl

ithreads	Build for use with thread-capable perl, needs same setting as in dev-lang/perl

mod_security

fuzzyhash	Support fuzzy hash computations (to detect malware, for example) using the app-crypt/ssdeep package.
geoip	Pull in dev-libs/geoip for use by the SecGeoLookupDb directive.
jit	Add support for the PCRE Just-in-Time optimisation, as enabled by dev-libs/libpcre with jit USE flag enabled. Might not be available on hardened systems.
json	Suppose JSON in the request body parser through dev-libs/yajl.
mlogc	Build and install the ModSecurity Audit Log Collector (mlogc).

pwauth

domain-aware	Ignore leading domain names in username (Windows compat)
faillog	Log failed login attempts
ignore-case	Ignore string case in username (mostly Windows compat)

www-apps

ampache

transcode	Install optional dependencies for transcoding support

blohg

git	Enable Git support
mercurial	Enable Mercurial support

bugzilla

extras	Optional Perl modules
modperl	Enable www-apache/mod_perl support

cgit

highlight	Enable source code highlighting
jit	If the lua flag is enabled, jit uses LuaJIT instead of vanilla Lua
lua	Enable support for Lua scripting

drupal

accelerator	Add dependency on a php accelerator
uploadprogress	Install dev-php/pecl-uploadprogress package

gitit

network-uri	Get Network.URI from the network-uri package.
plugins	enables optional plugin runtime loader

guacamole

noauth	enable support for leaving out any authentication on the webinterface

icingaweb2

nginx	Adds support for nginx

ikiwiki

extras	Installs additional modules used by ikiwiki plugins

klaus

ctags	Enable support for Exuberant ctags; makes all source code symbols hyperlinks to their definitions

nikola

assets	Support web asset management through dev-python/assets
charts	Support chart generation through dev-python/pygal
ghpages	Add support for direct uploading to github pages thru dev-python/ghp-import
hyphenation	Add hyphenation support through dev-python/pyphen
ipython	Add IPython notebook compilation and LESS support
jinja	Add support for dev-python/jinja as alternative templating engine to Mako
watchdog	Use dev-python/watchdog to monitor file system events
webmedia	Use dev-python/micawber to extract metadata from web media links
websocket	Add websocket support thru dev-python/ws4py

otrs

mod_perl	Provide all dependencies for use of mod_perl instead of cgi

postfixadmin

vacation	Install vacation.pl script and dependencies

redmine

markdown	Enable support for Markdown
passenger	Enable support for www-apache/passenger

rt

lighttpd	Add www-servers/lighttpd support

sitebar

plugins	Install optional plugins

sugarcrm

json	Add JSON (JavaScript Object Notation) support

trac

highlight	Enable syntax highlighting
i18n	Enable support for i18n with dev-python/Babel
restructuredtext	Enable support for reStructuredText for wiki formatting

tt-rss

daemon	Install additional init scripts for automated RSS updates

venus

django	Support for django template style to config files
genshi	Support for genshi style to config files
redland	Enable support for Redland RDF

viewvc

cvsgraph	Add dev-vcs/cvsgraph support to show graphical views of revisions and branches
mod_wsgi	Add www-apache/mod_wsgi support
pygments	Add dev-python/pygments support for syntax highlighting

webdavcgi

rcs	Adds support for a revision controlled backend with RCS (dev-vcs/rcs)

wordpress

akismet	Installs Akismet comment spam plug-in
themes	Installs themes (including default theme)

www-client

chromium

component-build	Split build into more shared libraries to speed up linking. Mostly intended for debugging and development, NOT RECOMMENDED for general use.
hangouts	Enable support for Google Hangouts features such as screen sharing
pic	Disable optimized assembly code that is not PIC friendly
proprietary-codecs	Enable proprietary codecs like H.264, MP3
suid	Build the SUID sandbox, which is only needed on CONFIG_USER_NS=n kernels
system-ffmpeg	Use system ffmpeg instead of the bundled one
system-icu	Use system icu instead of the bundled one
system-libvpx	Use system libvpx instead of the bundled one
tcmalloc	Use bundled tcmalloc instead of system malloc
widevine	Unsupported closed-source DRM capability (required by Netflix VOD)

elinks

bittorrent	Enable support for the BitTorrent protocol
brotli	Enable support for brotli compression
finger	Enable support for the finger protocol
gc	Enable garbage collection support via dev-libs/boehm-gc
gopher	Enable support for the gopher protocol
mouse	Make elinks to grab all mouse events
tre	Enable support for regex searches via dev-libs/tre
xml	Enable support for bookmarks via dev-libs/expat

firefox

bindist	Disable official Firefox branding (icons, name) which are not binary-redistributable according to upstream.
custom-optimization	Build with user-specified compiler optimizations (-Os, -O0, -O1, -O2, -O3) from CFLAGS (unsupported)
eme-free	Disable EME (DRM plugin) cabability at build time
gmp-autoupdate	Allow Gecko Media Plugins (binary blobs) to be automatically downloaded and kept up-to-date in user profiles
gtk2	Use the cairo-gtk2 rendering engine
hwaccel	Force-enable hardware-accelerated rendering (Mozilla bug 594876)
jemalloc	Enable or disable jemalloc
pgo	Add support for profile-guided optimization using gcc-4.5, for faster binaries. This option will double the compile time.
rust	Enable support for using rust compiler (experimental)
screenshot	Allow to disable screenshot extension in global profile
system-cairo	Use the system-wide x11-libs/cairo instead of bundled.
system-harfbuzz	Use the system-wide media-libs/harfbuzz and media-gfx/graphite2 instead of bundled.
system-icu	Use the system-wide dev-libs/icu instead of bundled.
system-jpeg	Use the system-wide media-libs/libjpeg-turbo instead of bundled.
system-libevent	Use the system-wide dev-libs/libevent instead of bundled.
system-libvpx	Use the system-wide media-libs/libvpx instead of bundled.
system-sqlite	Use the system-wide dev-db/sqlite installation with secure-delete enabled

google-chrome

plugins	Add system plugins path to launcher

google-chrome-beta

plugins	Add system plugins path to launcher

google-chrome-unstable

plugins	Add system plugins path to launcher

links

libevent	Enable dev-libs/libevent support

luakit

luajit	Use dev-lang/luajit instead of dev-lang/lua

lynx

gnutls	Use gnutls library for HTTPS support (openssl is the default library for HTTPS support).
ssl	Enable HTTPS support.

midori

granite	Enable support for the elementary library dev-libs/granite
zeitgeist	Add support for Zeitgeist event tracking system

netsurf

bmp	BMP bitmap image support (media-libs/libnsbmp)
duktape	Use duktape.org javascript engine
fbcon_frontend_able	Use framebuffer frontend able
fbcon_frontend_linux	Use framebuffer frontend linux
fbcon_frontend_sdl	Use framebuffer frontend sdl
fbcon_frontend_vnc	Use framebuffer frontend vnc
fbcon_frontend_x	Use framebuffer frontend X
gtk	Build GTK GUI, defaults to GTK3
gtk2	Build GTK2 GUI
gtk3	Build GTK3 GUI
pdf-writer	PDF output support (media-libs/libharu)
psl	Use public suffix list via media-libs/libnspsl
rosprite	RISC OS Sprite bitmap image support (media-libs/librosprite)
svgtiny	SVG image support via media-libs/svgatiny instead of gnome-base/librsvg
webp	WebP image support (media-libs/libwebp)

opera

gtk	Install support libraries and runtime dependencies to support GTK+/GNOME desktop integration

qupzilla

kwallet	Enable encrypted storage of passwords with kde-frameworks/kwallet
nonblockdialogs	Enable fancy non-blocking JavaScript dialogs shown inside the page, not blocking the application window. When closing browser windows with open dialogs, this can crash the application.

seamonkey

calendar	Build Mozilla's calendar
chatzilla	Build Mozilla's IRC client (default on)
custom-optimization	Build with user-specified compiler optimizations (-Os, -O0, -O1, -O2, -O3) from CFLAGS (unsupported)
force-gtk3	Use the cairo-gtk3 rendering engine
gmp-autoupdate	Allow Gecko Media Plugins (binary blobs) to be automatically downloaded and kept up-to-date in user profiles
ipc	Use inter-process communication between tabs and plugins. Allows for greater stability in case of plugin crashes
jemalloc	Enable or disable jemalloc
roaming	Build roaming extension support (default on)
system-cairo	Use the system-wide x11-libs/cairo instead of bundled
system-harfbuzz	Use the system-wide media-libs/harfbuzz instead of bundled
system-icu	Use the sytem-wide dev-libs/icu instead of bundled
system-jpeg	Use the system-wide media-libs/libjpeg-turbo instead of bundled
system-libevent	Use the system-wide dev-libs/libevent instead of bundled
system-libvpx	Use the system-wide media-libs/libvpx instead of bundled
system-sqlite	Use the system-wide dev-db/sqlite installation with secure-delete enabled

surf

savedconfig	Without a saved config.h, this package depends on net-misc/curl and x11-terms/st for a default download mechanism

uget

aria2	Enable support for net-misc/aria2 through xmlrpc. You'll find the plugin in the app's settings.
gtk3	Use x11-libs/gtk+:3 instead of x11-libs/gtk+:2
hide-temp-files	Make temporary files that are used while downloading hidden.

w3m

lynxkeymap	If you prefer Lynx-like key binding

weboob

fast-libs	Enable fast libs
secure-updates	Enable secure updates

www-misc

gurlchecker

json	Enable support for parsing Google Chrome and derivatives bookmarks.
sqlite	Enable support for parsing Firefox and derivatives bookmarks.

litmus

libproxy	Support for automatic proxy configuratino management through net-libs/libproxy.
libxml2	Use dev-libs/libxml2 to parse XML
pkcs11	Support for PKCS #11 through PaKChoiS (dev-libs/pakchois).

monitorix

apcupsd	Make use of a daemon that controls APC UPSes with sys-power/apcupsd.
httpd	Enables the CGI webserver with any package that satisfies virtual/httpd-cgi.
postfix	Analyze postfix logs with net-mail/pflogsumm.

shellinabox

pam	Enable PAM support.

vdradmin-am

vdr	Support for media-video/vdr. Disable this if the VDR you want to control runs at a remote machine.

xxv

themes	Enable more themes via x11-themes/xxv-skins

zoneminder

curl	Enable using net-misc/curl for streaming from cameras
gcrypt	...
vlc	Enable using media-libs/vlc for streaming from cameras

www-plugins

adobe-flash

nsplugin	Install the Netscape Flash API plugin (for Firefox and similar browsers)
ppapi	Install the Pepper Flash API plugin (for Chrome and similar browsers)

chrome-binary-plugins

widevine	Install the Widevine DRM library

freshplayerplugin

gles2	Use system GLESv2 libraries instead of ANGLE for shader translation
gtk3	Build with GTK+ 3 instead of GTK+ 2
v4l	Use libv4l2 for colorspace conversion

gnash

agg	Rendering based on the Anti-Grain Geometry Rendering Engine library
cygnal	Enable building of the cygnal server
dump	Enable dump output module for creating video from SWF
egl	Enable EGL support for the OpenVG, OpenGL and X11 renderers
harden	Enable upstream recommended hardening build flags (may conflict with system ones)
jemalloc	Use dev-libs/jemalloc for allocations
openvg	Rendering based on the OpenVG graphics acceleration API
sdl-sound	Enable SDL audio output for the standalone player
ssh	Enable using SSH for network authentication in libnet
ssl	Enable directly using OpenSSL in libnet (not needed for nsplugin ssl support)

lightspark

gles	Replace default OpenGL renderer with GLESv2
ppapi	Install the PPAPI plugin (for Chromium)
rtmp	Enable Real Time Messaging Protocol using librtmp

www-servers

apache

apache2_modules_access_compat	Group authorizations based on host (name or IP address). Available as a compatibility module with previous versions.
apache2_modules_authn_core	Provides core authentication capabilities common to all authentication providers (functionality provided by authn_alias in previous versions).
apache2_modules_authz_core	Provides core authorization capabilities to various authorization/authorization modules, such as authn_file and authz_user.
apache2_modules_authz_dbd	Provides authorization capabilities via SQL database so that authenticated users can be allowed or denied access to portions of the web site by group membership.
apache2_modules_cache_disk	Disk based storage module for the HTTP caching filter (similar to mem_cache in previous versions).
apache2_modules_cache_socache	Shared object cache (socache) based storage module for the HTTP caching filter.
apache2_modules_http2	Enable http2/alpn module
apache2_modules_lbmethod_bybusyness	Pending request counting load balancer scheduler algorithm for proxy_balancer.
apache2_modules_lbmethod_byrequests	Request counting load balancer scheduler algorithm for proxy_balancer.
apache2_modules_lbmethod_bytraffic	Weighted traffic counting load balancer scheduler algorithm for proxy_balancer.
apache2_modules_lbmethod_heartbeat	Heartbeat traffic counting load balancer scheduler algorithm for proxy_balancer.
apache2_modules_macro	Macros for the Apache config file.
apache2_modules_proxy_fcgi	FCGI support module for mod_proxy.
apache2_modules_proxy_html	Module to rewrite links in html pages behind a reverse proxy
apache2_modules_proxy_wstunnel	Provides support for the tunnelling of web socket connections to a backend websockets server.
apache2_modules_ratelimit	Ratelimit module for transfer rate management
apache2_modules_remoteip	Remotip module for logging
apache2_modules_slotmem_shm	Slot-based shared memory provider.
apache2_modules_socache_shmcb	A shared object cache provider using a high-performance cyclic buffer inside a shared memory segment.
apache2_modules_unixd	Basic (required) security for Unix-family platforms.
apache2_modules_watchdog	Provides infrastructure for other modules to periodically run tasks
apache2_modules_xml2enc	Enable xml2 encoding module
static	Link in apache2 modules statically rather then plugins
suexec	Install suexec with apache

cherokee

admin	Install web based cherokee conf tool
rrdtool	Enable rrdtool support

fnord

auth	Enable HTTP authentication support

gatling

diet	Compile against dev-libs/dietlibc

h2o

mruby	Enable support for mruby

hiawatha

cache	Enable caching of content
monitor	Pull in www-apps/hiawatha-monitor
rewrite	Enable the rewrite toolkit
rproxy	Enable reverse proxy support
ssl	Enable TLS support via net-libs/mbedtls
tomahawk	Enable Tomahawk control server
xslt	Enable XSLT support. This is also needed for directory listings

lighttpd

libev	Enable fdevent handler
mmap	Use mmap with files owned by lighttpd. This is a dangerous option as it may allow local users to trigger SIGBUS crashes.
rrdtool	Enable rrdtool support via mod_rrdtool
webdav	Enable webdav properties

monkeyd

debug	Enable lots of debugging info
static-plugins	Build statically linked plugins

nginx

aio	Enables file AIO support
http	Enable HTTP core support
http-cache	Enable HTTP cache support
http2	Enable HTTP2 module support
libatomic	Use libatomic instead of builtin atomic operations
luajit	Use dev-lang/luajit instead of dev-lang/lua for lua support when building the lua http module.
pcre-jit	Enable JIT for pcre
rtmp	NGINX-based Media Streaming Server
ssl	Enable HTTPS module for http. Enable SSL/TLS support for POP3/IMAP/SMTP for mail.

pound

dynscaler	Enable dynamic rescaling of back-end priorities

pshs

magic	Enable automatic detection of Content-Type using libmagic (sys-apps/file)
netlink	Use libnetlink (sys-apps/iproute2) to get network interface addresses
qrcode	Enable generating QRCodes for server URL

resin

admin	Enable Resin admin webapp

sniproxy

dns	Enable DNS resolver via net-libs/udns
largefile	Enable large file support (so we can log more than 2GB)
rfc3339	Use RFC3339 timestamp format in log.

tomcat

extra-webapps	Build also the docs and examples webapp
websockets	Builds websockets api and implementation (requires java 7)

uwsgi

embedded	Embed plugins instead of building them as real plugins. When disabling this USE flag make sure you specify all used plugins in your uWSGI configuration. Note: Language plugins will always be built as real plugins.
go	Build the gccgo plugin to run Go applications.
jemalloc	Use dev-libs/jemalloc instead of libc's malloc
json	Support json as a configuration file format.
pypy	Build the pypy plugin to run your code using virtual/pypy.
python_asyncio	Use the EXPERIMENTAL asyncio (tulip) for python3.4 async request dispatching and as LoopEngine (see http://uwsgi-docs.readthedocs.org/en/latest/asyncio.html).
python_gevent	Use dev-python/gevent for async request dispatching and as LoopEngine (see http://projects.unbit.it/uwsgi/wiki/Gevent).
routing	Enable routing support
yajl	Use dev-libs/yajl instead of dev-libs/jansson for parsing JSON configuration files (if USe=json is set)
yaml	Support yaml as a configuration file format.
zeromq	Enable logging and deployment via ZeroMQ.

varnish

jemalloc	Use dev-libs/jemalloc for allocations

xsp

developer	creates .mdb files for either Release and Debug
net35	use .NET 3.5 Framework
net40	use .NET 4.0 Framework
net45	use .NET 4.5 Framework

x11-apps

copyq

webkit	enables the application to use advanced HTML rendering and fetching remote images and other data

intel-gpu-tools

test-programs	Install test programs for DRM driver development
unwind	Provide automatic stack traces on test failures

mesa-progs

egl	Build EGL utilities
gles2	Build OpenGL ES 2 utilities

xdm

consolekit	Enable native sys-auth/consolekit support
xdm-auth	Enable XDM-AUTHENTICATION-1 support

xdpyinfo

dmx	Builds support for Distributed Multiheaded X x11-base/xorg-server

xinit

minimal	Control dependencies on legacy apps (xterm, twm, ...). Safe to enable if you use a modern desktop environment.

xsm

rsh	This allows the use of rsh (remote shell) and rcp (remote copy).

x11-base

xorg-server

dmx	Build the Distributed Multiheaded X server
glamor	Enable Glamor OpenGL 2D acceleration
kdrive	Build the kdrive X servers
tslib	Build with tslib support for touchscreen devices
unwind	Enable libunwind usage for backtraces
xcsecurity	Build Security extension
xephyr	Build the Xephyr server
xnest	Build the Xnest server
xorg	Build the Xorg X server (HIGHLY RECOMMENDED)
xvfb	Build the Xvfb server

x11-drivers

nvidia-drivers

X	Install the X.org driver, OpenGL libraries, XvMC libraries, and VDPAU libraries
compat	Install non-GLVND libGL for backwards compatibility
driver	Install the kernel driver module
gtk3	Install nvidia-settings with support for GTK+ 3
kms	Enable support for kernel mode setting (KMS)
pax_kernel	PaX patches from the PaX project
tools	Install additional tools such as nvidia-settings
uvm	Install the Unified Memory kernel module (nvidia-uvm) for sharing memory between CPU and GPU in CUDA programs

xf86-video-ati

glamor	Enable Glamor OpenGL 2D acceleration

xf86-video-geode

ztv	Enable building the V4L2 ZTV driver

xf86-video-intel

dri3	Use DRI3 by default
sna	Enable SandyBridge's New Acceleration (useful on all chipsets, not just SandyBridge)
tools	Build the intel-virtual-output tool
uxa	Enable UMA Acceleration Architecture
xvmc	Enables X-Video Motion Compensation support

xf86-video-openchrome

viaregtool	Install registers dumper tool

xf86-video-qxl

xspice	Build the xspice driver

x11-libs

agg

gpc	Enable gpc polygon clipper library

cairo

gles2	Build the OpenGL ES 2 backend
glib	Compile with GLib Object System support
opengl	Build the OpenGL backend
utils	Build support for Cairo script and trace utilities
valgrind	Built-in support to mark memory regions

fltk

games	Builds and installs some extra games

gdk-pixbuf

X	Build and install the legacy gdk_pixbuf_xlib-2.0 library

gtk+

broadway	Enable the GDK Broadway backend.
cloudprint	Enable printing via Google Cloud Print.
colord	Use x11-misc/colord for color management in printing

gtkdatabox

glade	Build with libglade and glade-3 supports, which includes a glade's module for GtkDataBox widget

gtkmathview

mathml	Install additional fonts for proper mathml support.
t1lib	Enable media-libs/t1lib support

gtksourceview

glade	Install a glade catalog file

libQGLViewer

designer	Installs dev-qt/designer plugin.

libSM

uuid	Use UUID for session identification instead of IP address and system time.

libXaw

deprecated	Install deprecated Xaw6 library.

libXfont

bzip2	Support bzip2 compressed PCF fonts.
truetype	Use media-libs/freetype for font rasterization.

libXfont2

bzip2	Support bzip2 compressed PCF fonts.
truetype	Use media-libs/freetype for font rasterization.

libaosd

pango	Enable the textual helpers (requires pangocairo).
tools	Install the aosd_cat tool (requires glib-2.0).

libdesktop-agnostic

gconf	Enable GConf as configuration backend
glade	Install the Glade catalog for the desktop-agnotstic GTK widgets.

libdrm

libkms	Enable building of libkms, a library for applications to interface with KMS
valgrind	Compile in valgrind memory hints

libfm

automount	Use gnome-base/gvfs for automounting
udisks	Use libfm's udisks-based volume monitor implementation instead of using the one from gvfs
vala	Support custom actions in menus

libqxt

berkdb	Build the QxtBerkeley module
sql	Build the QxtSql module
web	Build the QxtWeb module
zeroconf	Build the QxtZeroconf module

libva

drm	Enables VA/DRM API support.
egl	Enables EGL support.
utils	Install VA-API utility programs.

libva-intel-driver

drm	Enables VA/DRM API support.

libwnck

tools	Install wnckprop-3 and wnck-urgency-monitor-3 command-line tools

libxcb

xkb	Enable the XCB keyboard extension

motif

motif22-compatibility	Compatibility with Open Motif 2.2

pango

X	Build and install the legacy pangoxft library

pixman

loongson2f	Enable Loongson2f MMI optimizations.

qscintilla

designer	Build plugin for Qt Designer

qwt

designer	Installs dev-qt/designer plugin.
mathml	Use the MathML renderer of the Qt solutions package.

vte

glade	Provide integration with dev-util/glade.

wxGTK

gnome	Use gnome-base/libgnomeprintui for printing tasks.
gstreamer	Enable the wxMediaCtrl class for playing audio and video through gstreamer.
sdl	Use Simple Directmedia Layer (media-libs/libsdl) for audio.

x11-misc

alock

doc	Build and install manpage with app-text/asciidoc.

bumblebee

bbswitch	Add dependency on sys-power/bbswitch for PM feature

cdm

consolekit	Enable native consolekit support

colord

argyllcms	Enable ArgyllCMS sensor
extra-print-profiles	Generate extra print profiles. Warning: significant build time and memory requirements.
gusb	Enable dev-libs/libgusb support, needed for colorimeter drivers

compton

drm	Enable VSync with DRM_IOCTL_WAIT_VBLANK
opengl	Enable VSync with SGI_swap_control OpenGL extension

dunst

dunstify	Experimental replacement for notify-send.

fbpager

xrender	Enable transparency support via x11-libs/libXrender

gpaste

applet	Enable gpaste-applet
gnome	Enable proper gnome support and enable gnome shell extension.

gtkdialog

glade	Enable support for gnome-base/libglade
vte	Enable support for x11-libs/vte

i3status

filecaps	Linux capabilities library is required for i3status to be able to read net bandwith

ktsuss

sudo	Use the sudo backend instead the su one

light-locker

consolekit	Keep track of the various users, sessions, and seats present on the system.
dpms	Turn on the display on screensaver deactivation.
gtk3	Build with GTK+ 3 instead of GTK+ 2.
screensaver	Lock the screen on screensaver activation.

lightdm

gtk	Pull in the gtk+ greeter

mate-notification-daemon

gtk3	Build with GTK+3 instead of GTK+2

mozo

gtk3	Build with GTK+3 instead of GTK+2

openbox-menu

icons	Enable support for icons in menus
svg	Support SVG icons

qt5ct

dbus	Enable system tray and global menu support
systray	Enable system tray support

redshift

appindicator	Enable usage of dev-libs/libappindicator to export menu options in to unity and KDE 5
geoclue	Control dependency on app-misc/geoclue

rofi

windowmode	Enable normal window mode

rss-glx

quesoglc	Enable support for OpenGL Character Renderer

sddm

consolekit	Use ck-launch-session from sys-auth/consolekit by default in Xsession (no native support)
elogind	Use sys-auth/elogind for session tracking.

sent

savedconfig	Without a saved config.h, this package depends on media-gfx/farbfeld for image conversions

shutter

drawing	Enables drawing tool

slim

consolekit	Enable native consolekit support

spacefm

gtk2	Support GTK+ 2.x instead of GTK+ 3.x
gtk3	Support GTK+ 3.x instead of GTK+ 2.x
video-thumbnails	Support video thumbnails with media-video/ffmpegthumbnailer

stalonetray

graceful-exit	use non-portable hack to exit gracefuly on signal

tint2

battery	Enable battery status plugin
tint2conf	Build/Install tint2conf as well

vnc2swf

x11vnc	Install script that depends on x11vnc

wbar

gtk	Enables the gtk-based wbar-config GUI

xkbset

tk	Install the dev-perl/Tk based xkbset-gui utility

xlockmore

vtlock	Enables support for virtual terminal locking
xlockrc	Enables xlockrc for people without PAM

xmobar

mpd	Support mpd plugin
mpris	Enables MPRIS v1, v2 support
timezone	Enables localized date support
with_conduit	Use conduit to fetch weather data.
with_uvmeter	Plugin to show UV data for Australia.

xscreensaver

gdm	Use gdmflexiserver from gnome-base/gdm instead of x11-misc/lightdm
new-login	Enable user switching support using gdmflexiserver (x11-misc/lightdm)

xsr

cursor	Capture mouse cursor using x11-misc/xdotool, and place them on the screenshots using media-gfx/imagemagick

xss-lock

man	Build and install man pages

x11-plugins

bfm

gkrellm	Enable building of app-admin/gkrellm module

compiz-plugins-extra

gconf	Install GConf schemas for the plugins, needed when using the GConf-based configuration backend in x11-wm/compiz.

compiz-plugins-main

gconf	Install GConf schemas for the plugins, needed when using the GConf-based configuration backend in x11-wm/compiz.

pidgin-mbpurple

twitgin	Enable graphical plugin for Gtk+ interface of Pidgin.

pidgin-sipe

ocs2005-message-hack	Disable message timeout for OCS2005 clients which causes "false" not delivered error messages
openssl	Enable crypto support via dev-libs/openssl
telepathy	Support use as a telepathy backend
voice	Enable experimental voice/video support

purple-plugin_pack

talkfilters	Enable support for app-text/talkfilters

vicious

contrib	Install extra widgets, some for less common hardware, some contributed by Vicious users.

wmfire

session	Enable session management

wmsysmon

high-ints	Enable support for monitoring 24 interrupts. Useful on SMP machines

x11-terms

aterm

background	Enable background image support via media-libs/libafterimage
xgetdefault	Enable resources via X instead of aterm small version

eterm

escreen	Enable built-in app-misc/screen support
utempter	Include libutempter support

gnome-terminal

gnome-shell	Integrate with gnome-base/gnome-shell search
nautilus	Build gnome-base/nautilus extension

hanterm

utempter	Records user logins. Useful on multi-user systems

mate-terminal

gtk3	Build with GTK+3 instead of GTK+2

mlterm

fcitx	Enable support for app-i18n/fcitx
gtk2	Build with x11-libs/gtk+:2 instead of x11-libs/gtk+:3
harfbuzz	Enable support for OpenType Layout (media-libs/harfbuzz)
ibus	Enable support for app-i18n/ibus
libssh2	Enable support for net-libs/libssh2
regis	Enable support for ReGIS
scim	Enable support for app-i18n/scim
skk	Enable support for SKK (virtual/skkserv or app-i18n/skk-jisyo)
uim	Enable support for app-i18n/uim
utempter	Enable support for sys-libs/libutempter

mrxvt

menubar	Enable mrxvt menubar
utempter	REcords user logins. Useful on multi-user systems

rxvt-unicode

256-color	Enable 256 color support
alt-font-width	Calculate the font width using a different method
blink	Enable blinking text
buffer-on-clear	Store visible output to history buffer when clearing the screen with ctrl-l. Read https://bbs.archlinux.org/viewtopic.php?id=129302
fading-colors	Enable colors fading when off focus
focused-urgency	Enable the urgent flag when a terminal window is focused
font-styles	Enable support for bold and italic fonts
iso14755	Enable ISO-14755 support
mousewheel	Enable scrolling via mouse wheel or buttons 4 and 5
perl	Enable perl script support. You can still disable this at runtime with -pe ""
pixbuf	Enable transparency support using gtk's pixbuf
secondary-wheel	Support for wheel scrolling on secondary screens (like mutt). Read http://lists.schmorp.de/pipermail/rxvt-unicode/2011q4/001491.html
unicode3	Use 21 instead of 16 bits to represent unicode characters
wcwidth	Enable wide char width support

terminator

libnotify	Enables desktop notifications viadev-python/notify-python

xterm

openpty	Use openpty() in preference to posix_openpt()
toolbar	Enable the xterm toolbar to be built

x11-themes

arc-theme

cinnamon	Install theme for gnome-extra/cinnamon
gnome-shell	Install theme for gnome-base/gnome-shell
gtk2	Install GTK+2 theme
gtk3	Install GTK+3 theme
mate	Install Metacity theme for mate-base/mate
xfce	Install theme for xfce-base/xfwm4

comix-xcursors

lefthanded	Install lefthanded version of theme in addition to default one
opaque	Install non-transparent version of theme in addition to default one

gentoo-artwork

grub	Install extra sys-boot/grub themes
icons	Install icons
lilo	Install extra sys-boot/lilo themes
pixmaps	Install pixmaps

gtk-engines-murrine

animation-rtl	Progressbar animation from right to left
themes	Pull in themes via x11-themes/murrine-themes

gtk-engines-nodoka

animation-rtl	Progressbar animation from right to left

kfaenza

additional	Install additional KFaenza icons. See third homepage for details

light-themes

gtk3	Support GTK 3.x, too

mate-themes-meta

gtk2-only	Allow dependency-resolution for a system without GTK+3

redhat-artwork

audacious	Install media-sound/audacious theme
cursors	Install Bluecurve cursors
gdm	Install Bluecurve gnome-base/gdm theme
icons	Install Bluecurve icons
nautilus	Install Bluecurve gnome-base/nautilus icons

skinenigmang-logos

dxr3	Install logos for lower osd color depth on dxr3 cards

vertex-theme

cinnamon	Install theme for gnome-extra/cinnamon
gnome-shell	Install theme for gnome-base/gnome-shell
mate	Install Metacity theme for mate-base/mate
xfce	Install theme for xfce-base/xfwm4

zuki-themes

gnome-shell	Install theme for gnome-base/gnome-shell
mate	Install Metacity theme for mate-base/mate
xfce	Install theme for xfce-base/xfwm4

zukitwo

gnome-shell	Install theme for gnome-base/gnome-shell

x11-wm

awesome

luajit	Use dev-lang/luajit instead of dev-lang/lua

compiz

fuse	Enables support for the filesystem in userspace plugin through sys-fs/fuse.
gconf	Enable the GConf-based configuration backend; it is not required to work with GNOME, and might actually be faster if it's not used.

compiz-fusion

emerald	Install the x11-wm/emerald package.
unsupported	Install the x11-plugins/compiz-plugins-unsupported package.

echinus

xrandr	Enable support for multihead configuration

enlightenment

enlightenment_modules_appmenu	Gadget that hold the toolbar of the foreground application
enlightenment_modules_backlight	Backlight control slider gadget
enlightenment_modules_battery	A gadget to visualize your battery status
enlightenment_modules_bluez4	Configure Bluetooth devices
enlightenment_modules_clock	Nice clock gadget to show current time
enlightenment_modules_conf	Settings Panel
enlightenment_modules_conf-applications	Allows configuration of Ibar, Restart, and Startup applications
enlightenment_modules_conf-bindings	Input Control Settings
enlightenment_modules_conf-dialogs	Configure default dialog properties
enlightenment_modules_conf-display	Used to configure your screen
enlightenment_modules_conf-interaction	Configure Mouse and Touch input
enlightenment_modules_conf-intl	Used to select a default language
enlightenment_modules_conf-menus	Configures menu behavior
enlightenment_modules_conf-paths	Specifies the Enlightenment search paths and default directories
enlightenment_modules_conf-performance	Used to configure certain performance related items as frame rates and cache settings
enlightenment_modules_conf-randr	Used to configure your screen's resolution
enlightenment_modules_conf-shelves	Shelf configuration dialog
enlightenment_modules_conf-theme	Used to configure your theme preferences
enlightenment_modules_conf-window-manipulation	Configures window raise, resistance, and maximize policies
enlightenment_modules_conf-window-remembers	Delete existing window remembers
enlightenment_modules_connman	Control Wifi and wired networks as a user
enlightenment_modules_cpufreq	Gadget to monitor and change the CPU frequency
enlightenment_modules_everything	The run command module provides an application launcher dialog
enlightenment_modules_fileman	Enlightenment's integrated file manager
enlightenment_modules_fileman-opinfo	Can be placed on the desktop or in a shelf
enlightenment_modules_gadman	Module to manage gadgets on the desktop
enlightenment_modules_geolocation	Geolocation
enlightenment_modules_ibar	Iconic application launcher
enlightenment_modules_ibox	A home for your iconified applications
enlightenment_modules_lokker	Screen locker
enlightenment_modules_mixer	A module to provide a mixer for changing volume
enlightenment_modules_msgbus	DBus Extension
enlightenment_modules_music-control	Control your music in your shelf
enlightenment_modules_notification	notification-daemon alternative. Popup if an event occur
enlightenment_modules_packagekit	Package manager integration
enlightenment_modules_pager	Gadget to allow you to visualize your virtual desktops and the windows they contain
enlightenment_modules_pager-plain	A simpler desktop pager
enlightenment_modules_policy-mobile -
enlightenment_modules_quickaccess	Enlightenment Quickaccess Launcher
enlightenment_modules_shot	Simple screenshot+save/upload module
enlightenment_modules_start	Enlightenment's 'Start' button equivalent
enlightenment_modules_syscon	This module provides a unified popup dialog for all the system actions in Enlightenment
enlightenment_modules_systray	system tray that hold applications icons like Skype, Pidgin, Kopete and others
enlightenment_modules_tasks	Gadget to allow you to switch tasks
enlightenment_modules_teamwork	Enable teamwork module
enlightenment_modules_temperature	Temperature monitor
enlightenment_modules_tiling	Positions/resizes your windows tilingly
enlightenment_modules_time	Time related gadgets
enlightenment_modules_winlist	A module to show the list of client applications presently running
enlightenment_modules_wireless	WiFi monitoring
enlightenment_modules_wizard	First Run Wizard
enlightenment_modules_wl-desktop-shell	Enlightenment Wayland Desktop Shell
enlightenment_modules_wl-drm	Wayland DRM (Direct Rendering Manager) compositing module
enlightenment_modules_wl-text-input	Wayland text input support
enlightenment_modules_wl-weekeyboard	Wayland virtual keyboard
enlightenment_modules_wl-wl	Wayland-in-Wayland module
enlightenment_modules_wl-x11	Wayland-in-X11 module
enlightenment_modules_xkbswitch	Keyboard layout configuration and switcher
enlightenment_modules_xwayland	X/Wayland integration
pango	Enable pango font rendering
ukit	Use upower/udisks to automount devices
xrandr	Enable support for the X xrandr extension

fluxbox

bidi	Enable bidirectional language support with dev-libs/fribidi
slit	Enables the Fluxbox slit (or dock)
systray	Enables the system tray in the Fluxbox toolbar
toolbar	Enables the Fluxbox toolbar

fvwm

gtk2-perl	Enable GTK2 Perl bindings
lock	Enable screen locking
netpbm	Enable NetPBM support (used by FvwmScript-ScreenDump)
rplay	Enable rplay support
stroke	Mouse Gesture support

i3

doc	Build and install the HTML documentation and regenerate the man pages

lumina

desktop-utils	Build and install lumina's desktop-utils

marco

gtk3	Build with GTK+3 instead of GTK+2

musca

apis	Optionally install the experimental `apis' window manager
xlisten	Optionally install the xlisten utility

mutter

gles2	Enable OpenGL ES 2.0 support

notion

xrandr	Add support for xrandr

openbox

session	Enables support for session managers
xdg	Install the python xdg files for xdg autostart

pekwm

contrib	Install optional extras in the documentation directory
themes	Install additional themes

ratpoison

history	Use sys-libs/readline for history handling
sloppy	Install sloppy, a focus-follows-mouse implementation for ratpoison
xrandr	Enable support for XRandR

stumpwm

clisp	Use CLISP for the runtime
contrib	Install contrib modules
doc	Include documentation
ecl	Use SCL for the runtime
emacs	Add support for GNU Emacs
sbcl	Use SBCL for the runtime

subtle

xrandr	Enable support for the X RandR extension
xtest	Enable support for the XTest extension

vtwm

rplay	Enable rplay support, needed for sound.

windowmaker

modelock	Enable XKB language status lock support. README says: "If you don't know what it is you probably don't need it."
webp	Enables WebP image format support using media-libs/libwebp
xrandr	Enable XRandR window extension support

wmfs

imlib2	Enable image support through media-libs/imlib2

xmonad

default-term	Pull terminal specified in default xmonad config to be a bit less hostile by default.
no-autorepeat-keys	Allow ignoring of keyboard autorepeat.

xpra

client	Build client-side code
clipboard	Enable clipboard support
csc	Enable csc softscaler support
dec_avcodec2	Enable avcodec2 decoder support
enc_ffmpeg	Enable advanced ffmpeg/libav encoder support
enc_x264	Enable x264 encoder support
enc_x265	Enable x265 encoder support
lz4	Enable support for lz4 compression
pillow	Enable pillow support
server	Build server-side code
vpx	Enable vpx image format support
webcam	Enable webcam support via opencv
webp	Enable webp image format support

xfce-base

garcon

gtk2	Build the garcon-gtk2-1 library (required for xfce-base/xfce4-panel < 4.13 only).

libxfce4ui

glade	Build support for Glade 3's GtkBuilder implementation

thunar

trash-panel-plugin	Build the trash status indicator plugin for the XFCE panel

xfce4-settings

libcanberra	Enable sound event support using media-libs/libcanberra
xklavier	Enable keyboard layout selection support using x11-libs/libxklavier

xfdesktop

thunar	Build support for desktop icons (for example, launchers and folders)

xfwm4

xpresent	Enable the XPresent extension for sync to vblank

xfce-extra

tumbler

odf	Enable support for .odf thumbnailers by using gnome-extra/libgsf

xfce4-clipman-plugin

qrcode	Enable support for media-gfx/qrencode

xfce4-mpc-plugin

libmpd	Build using media-libs/libmpd backend, instead of native fallback which is preferred

xfce4-playercontrol-plugin

audacious	Enable Audacious support
mpd	Enable Music Player Daemon support

xfce4-power-manager

panel-plugin	Build the power management plugin for the XFCE panel

xfce4-pulseaudio-plugin

keybinder	Enable support for global hotkeys using dev-libs/keybinder.
wnck	Enable experimental support for raising media player windows using x11-libs/libwnck.

xfce4-soundmenu-plugin

glyr	Enable music metadata searchengine support using media-libs/glyr
keybinder	Enable shortcut support using dev-libs/keybinder
lastfm	Enable last.fm support using media-libs/libclastfm

xfce4-taskmanager

gksu	Build against x11-libs/libgksu to provide "Run as root" option in the application's menu
gtk3	Use GTK+3 instead of GTK+2

xfswitch-plugin

gdm	Compatibility with gnome-base/gdm only
lightdm	Compatibility with x11-misc/lightdm only
lxdm	Compatibility with lxde-base/lxdm only