Gobject-based plugins engine (Peas 1.0 API)

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

Library for parsing, formatting, and validating phone numbers

https://github.com/google/libphonenumber

Library to deal with pinyin

https://github.com/libpinyin/libpinyin

Reusable library for GPU-accelerated video/image rendering

https://code.videolan.org/videolan/libplacebo

Library to handle Apple Property List format

http://www.libimobiledevice.org

GIO-styled async APIs for Flatpak

https://github.com/flatpak/libportal

GIO-styled async APIs for Flatpak

https://github.com/flatpak/libportal

GIO-styled async APIs for Flatpak

https://github.com/flatpak/libportal

GIO-styled async APIs for Flatpak

https://github.com/flatpak/libportal

GIO-styled async APIs for Flatpak (qt6 backend)

https://github.com/flatpak/libportal

Library for transforming bitmaps into vector graphics

http://potrace.sourceforge.net

Library that provides automatic proxy configuration management

https://libproxy.github.io/libproxy/

C library to handle the Public Suffix List

https://github.com/rockdaboot/libpsl

This library provides weak aliases for pthread functions

https://xcb.freedesktop.org/

OS independent and secure pseudo-tty management

http://software.schmorp.de/pkg/libptytty.html

Backend library for the Pidgin multi-protocol messaging client

https://www.pidgin.im/

Library for generating random passwords and quality checking

https://github.com/libpwquality/libpwquality

Helper to make writing accessibility tools easier

https://api.kde.org/libqaccessibilityclient/html/index.html

Multi-purpose desktop calculator (backend library)

http://qalculate.github.io/

C library for encoding data in a QR Code symbol

http://megaui.net/fukuchi/works/qrencode/index.en.html

Library that encapsulates complex text layout logic

https://github.com/HOST-Oman/libraqm

Library for manipulating raw images

https://www.libraw.org/

Free version of the SSL/TLS protocol forked from OpenSSL

http://www.libressl.org/

Easy access to RESTful web services

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

GNOME REST library

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

TLS library designed to ease writing foolproof applications

https://git.causal.agency/libretls/about/

Base library for writing document import filters

http://libwpd.sourceforge.net

Library for Reliable Internet Stream Transport (RIST) protocol

https://code.videolan.org/rist/librist

Library for parsing and rendering SVG vector-graphic files

http://live.gnome.org/LibRsvg

Library for parsing and rendering SVG vector-graphic files

http://live.gnome.org/LibRsvg

Library for delta compression of streams

https://github.com/librsync/librsync

RT Topology Library

https://git.osgeo.org/gitea/rttopo/librttopo

Secret Rabbit Code: a Sample Rate Converter for audio

http://www.mega-nerd.com/SRC/

C/C++ implementation of a Sass compiler

http://libsass.org/

C++ implementation of 3mf loading/python bindings

https://github.com/Ultimaker/libSavitar

Library to access the secret service API

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

Connect and transmit data to an Icecast media streaming server

http://www.icecast.org/

GTK4 widget to display maps

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

Commodore SID-chip emulator library to play SID music files

Callback Framework for C++

http://libsigc.sourceforge.net/

Callback Framework for C++

https://libsigcplusplus.github.io/libsigcplusplus/index.html

Implementation of the Signal client protocol

https://github.com/signalapp/libsignal-client

Handling page faults in user mode

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

Complete 2D graphic library for drawing Text, Geometries, and Images

https://skia.org/

Library to deal with Japanese Kana-to-Kanji conversion method

https://github.com/ueno/libskk

Routines for rapid alpha-numeric terminal applications development

http://www.s-lang.org/

Routines for rapid alpha-numeric terminal applications development

http://www.jedsoft.org/slang/

General purpose TCP-IP emulator library

https://gitlab.freedesktop.org/slirp/libslirp

Library to access SMI MIB information

http://www.ibr.cs.tu-bs.de/projects/libsmi/

Reading and writing files containing sampled sound (like WAV or AIFF)

http://www.mega-nerd.com/libsndfile/