Implementation of a VT220/xterm/ECMA-48 terminal emulator

https://www.leonerd.org.uk/code/libvterm/

Adds tablet support to libinput

http://linuxwacom.sourceforge.net/wiki/index.php/Libwacom

String internment library

https://www.netsurf-browser.org/projects/libwapcaplet/

C library for lightweight websocket clients and servers

https://libwebsockets.org/

Tools and library for converting Microsoft WMF (windows metafile)

http://wvware.sourceforge.net/libwmf.html

Tools and library for converting Microsoft WMF (windows metafile)

http://wvware.sourceforge.net/libwmf.html

Library used for writing pagers and taskslists

http://www.gnome.org/

Library used for writing pagers and taskslists

http://www.gnome.org/

Tools for importing and exporting WordPerfect(tm) documents

http://libwpd.sourceforge.net/

Tools for importing and exporting WordPerfect(tm) documents

http://libwpd.sourceforge.net/

General-purpose library for WPE WebKit

https://wpewebkit.org/releases

Library and tools to work with WordPerfect Graphics (WPG) files

https://libwpg.sourceforge.net/

Window Maker raster graphics library

http://www.windowmaker.org/

The W3C Reference Library

http://www.w3.org/Library/

Library for encoding H.264/MPEG-4 AVC video

http://www.videolan.org/x264.html

3D Xaw (Athena Widget Set) replacement with extended fonts

https://sourceforge.net/projects/sf-xpaint/files/

The X protocol C-language Binding (XCB) library

http://xcb.freedesktop.org/

Extended crypt library for descrypt, md5crypt, bcrypt, and others

https://github.com/besser82/libxcrypt

Calculate VESA CVT mode lines

https://gitlab.freedesktop.org/xorg/lib/libxcvt

Implementation of the XDG Base Directory specification

http://n.ethz.ch/student/nevillm/download/libxdg-basedir/

Widgets library for the Xfce desktop environment

http://www.xfce.org/

Extension library for the Xfce desktop environment

http://www.xfce.org/

Windowing concept abstraction library for X11 and Wayland

https://gitlab.xfce.org/xfce/libxfce4windowing

Libraries for xine multimedia player

https://www.xine-project.org/

Keymap handling library for toolkits and window systems

http://xkbcommon.org/

XKB file library

https://www.freedesktop.org/Software/xorg

Utility library to make XKB stuff easier

http://gswitchit.sourceforge.net/

XML API for C++

http://libxmlplusplus.sourceforge.net/

XML parser library for GNOME

http://xmlsoft.org/

Python interface for XML parser library for GNOME

http://xmlsoft.org/

Library to help create and query binary XML blobs

https://github.com/hughsie/libxmlb

Module rendering library for xmp

http://xmp.sourceforge.net/

XSD runtime library

https://www.codesynthesis.com/projects/xsd/

W3C XML Schema compiler frontend

https://www.codesynthesis.com/projects/libxsd-frontend/

Shared memory 'SyncFence' synchronization primitive

http://www.freedesktop.org/Software/xlibs

The XSLT C library for GNOME

http://xmlsoft.org/XSLT/

YAML 1.1 parser and emitter written in C

http://pyyaml.org/wiki/LibYAML

YANG data modeling language library, version 2

https://github.com/CESNET/libyang

Library for decrypting and parsing YubiKey One-Time Passwords

https://developers.yubico.com/yubico-c/

Library for freeswitch yuv graphics manipulation

https://chromium.googlesource.com/libyuv/libyuv/

GLib/GObject wrapper for the Skydrive and Hotmail API

https://github.com/GNOME/libzapojit

ZenLib used by MediaInfo and its library

https://mediaarea.net/en/MediaInfo https://github.com/MediaArea/ZenLib

Reference implementation of the ZIM specification

https://wiki.openzim.org/wiki/Libzim

C library for reading, creating, and modifying ZIP archives

http://www.nih.at/libzip/

Library that parses the file format of Zoner Callisto/Draw documents

https://wiki.documentfoundation.org/DLP/Libraries/libzmf

ZeroMQ core library (Version 4)

https://www.zeromq.org/

C client interface to Zookeeper server

https://zookeeper.apache.org/

GNU ZRTP library

https://github.com/wernerd/ZRTPCPP

Routines to access raw VBI capture devices

http://zapping.sourceforge.net/doc/libzvbi/

Simple RSS/RDF feed reader

https://lzone.de/liferea/