GLib based implimentation of the GData protocol

http://live.gnome.org/libgdata

GDI+ API for System.Windows.Forms in Mono

https://www.mono-project.com/docs/gui/libgdiplus/

GObject collection library

https://wiki.gnome.org/Projects/Libgee

GObject based library for handling and rendering epub documents

https://gitlab.gnome.org/GNOME/libgepub

The GGZ Gaming Zone - Base Library

http://www.ggzgamingzone.org/

Gigasampler file loader library

http://www.linuxsampler.org/

Portable, pure C implementation of the Git core

https://libgit2.github.com/

Glib wrapper library around the libgit2 git access library

https://git.gnome.org/browse/libgit2-glib

Library providing su and sudo functionality

http://www.gnu.org/non-gnu/gksu/

GNOME glade library

GL Vendor-Neutral Dispatch library

https://gitlab.freedesktop.org/glvnd/libglvnd

Collection of video game music emulators

https://bitbucket.org/mpyne/game-music-emu

Small library intended for internal use by GNOME Games

https://git.gnome.org/browse/libgnome-games-support

Program that keeps passwords and other secrets

Graphics library for GNOME

GNOME keyboard shared library

Toolkit based on glib and ncurses for text-mode user interfaces

https://keep.imfreedom.org/libgnt/libgnt/

GNU Regex Library

http://www.gnu.org/software/gnulib/

Common error values for all GnuPG components

https://www.gnupg.org/software/libgpg-error/

Universal digital camera control library

http://www.gphoto.org/proj/libgphoto2/

Library for direct access to iPod/iPhone contents

http://www.gtkpod.org/wiki/Libgpod

Library for easy management of RSS/Atom/Pie feeds

http://www.gnome.org/

GNU SASL library

https://www.gnu.org/software/gsasl/

Extensible i/o abstraction for dealing with structured file formats

http://www.gnumeric.org

GNOME top library

https://gitlab.gnome.org/GNOME/libgtop

GObject bindings for libudev.

https://wiki.gnome.org/Projects/libgudev

Library to access online weather informations

http://www.gnome.org/

GObject based library for rendering XPS documents

https://wiki.gnome.org/action/show/Projects/libgxps

Library with GTK+ widgets for mobile phones

https://gitlab.gnome.org/GNOME/libhandy/

Library with GTK+ widgets for mobile phones

https://source.puri.sm/Librem5/libhandy

HTML5 parser library

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

Implementation of the IETF Calendaring and Scheduling protocols

https://github.com/libical

Character set conversion library

https://www.gnu.org/software/libiconv/

ID3 tags library (part of MAD project)

http://mad.sourceforge.net/

Internationalized Domain Names command line tool

http://www.gnu.org/software/libidn

Implementation of IDNA2008 internationalized domain names

https://www.gnu.org/software/libidn/#libidn2 https://gitlab.com/libidn/libidn2

C library that supports plugin printer driver for Ghostscript

http://www.linuxprinting.org/ijs/

Library to communicate with Apple iOS devices

http://www.libimobiledevice.org

Kevent based inotify compatible library

https://github.com/libinotify-kqueue/libinotify-kqueue

Generic input library

https://www.freedesktop.org/wiki/Software/libinput/

ODBC 3.x driver manager, for universal data source access

http://www.iodbc.org/

Library for manipulating IPTC metadata stored in image files

http://libiptcdata.sourceforge.net/

Library for Evation's Irman infrared receiver

https://libirman.sourceforge.io/

Libburnia ISO9660 filesystem creation library

https://dev.lovelyhq.com/libburnia/web/wikis/home

Standalone client/server 9P library

https://libs.suckless.org/deprecated/libixp/

SIMD-accelerated JPEG codec library, provides libTurboJPEG

https://libjpeg-turbo.org/

Codec for karaoke and text encapsulation for Ogg

https://wiki.xiph.org/index.php/OggKate

Library to make X.509 certificates

https://www.gnupg.org/aegypten2/

Interface library to access tags for identifying languages

http://tagoh.bitbucket.org/liblangtag/

Lightweight Open Sound Control implementation

http://liblo.sourceforge.net/