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

Weak aliases for pthread functions

https://xcb.freedesktop.org/

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

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

Cross-platform library for parsing flash media stream URLs

http://quvi.sourceforge.net/

Embedded lua scripts for libquvi and utility scripts

http://quvi.sourceforge.net/

Embedded lua scripts for libquvi and utility scripts

http://quvi.sourceforge.net/

Cross-platform library for parsing flash media stream URLs

http://quvi.sourceforge.net/

Library that encapsulates complex text layout logic

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

Library for manipulating raw images

https://www.libraw.org/

Autodiscovering PHP/MySQL/SNMP based network monitoring

https://www.librenms.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

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

RTMP stream library

https://rtmpdump.mplayerhq.hu/

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/

Library to access the secret service API

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

Extension widgets for GTK+

http://releases.chipx86.com/libsexy/libsexy/

Connect and transmit data to an Icecast media streaming server

https://icecast.org/

Commodore SID-chip emulator library to play SID music files

Callback Framework for C++

http://libsigc.sourceforge.net/

Implementation of the Signal client protocol

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

Handling page faults in user mode

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

Routines for rapid alpha-numeric terminal applications development

https://www.jedsoft.org/slang/

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/

Library to build higher-level cryptographic tools

https://github.com/jedisct1/libsodium

SOAP (Simple Object Access Protocol) implementation in C

https://libsoup.org/

HTTP client/server library for GNOME

High quality, one-dimensional sample-rate conversion library

http://sourceforge.net/p/soxr/

Small library for rendering Postscript documents

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

Sender Policy Framework (SPF) library and client

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

Sender Rewriting Scheme 2 C Implementation

https://www.libspf2.org/

Implements the server side of the SPICE protocol

https://spice-space.org/

Library to convert clothoid splines into Bezier splines

https://github.com/fontforge/libspiro

Secure RTP (SRTP) Reference Implementation

https://github.com/cisco/libsrtp

Library implementing the SSH2 protocol

https://www.libssh.org/

Library implementing the SSH2 protocol

https://www.libssh2.org/

Provides a useful interface to system statistics

https://libstatgrab.org/

Wrapper providing SunOS NFSv4 ACL API