Memory hard password hashing program and library

https://github.com/P-H-C/phc-winner-argon2

Atomic operations access library

http://www.hboehm.info/gc/

Sound library for SGI audio file

http://www.68k.org/~michael/audiofile/

C library implementing the Cangjie input method

https://github.com/Cangjians/libcangjie

Cascading Style Sheets library

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

C++ utility library with generic and independent components

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

Free DTS Coherent Acoustics decoder

http://www.videolan.org/developers/libdca.html

Open source h.265 video codec

https://www.libde265.org

Generic Device Query and Monitor interface

https://github.com/freebsd/libdevq

MPlayer version of the libdvdnav project

http://dvdnav.mplayerhq.hu

MPlayer version of the libdvdread project

http://dvdnav.mplayerhq.hu

Command line editor library

http://thrysoee.dk/editline/

Library for some string essentials

https://libestr.adiscon.com/

API for executing callback functions on events or timeouts

http://libevent.org/

Library to read digital camera file meta-data

http://sourceforge.net/projects/libexif/

Language guessing by N-Gram-Based Text Categorization

https://wiki.documentfoundation.org/Libexttextcat

Fork of json-c (JSON implementation in C)

https://github.com/rsyslog/libfastjson

GNU Regex Library

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

Common code used by the libimobiledevice project

https://www.libimobiledevice.org

Kevent based inotify compatible library

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

Provides a few data structures and helpful functions

https://github.com/cheusov/libmaa

Library for the MaxMind DB file format used for GeoIP2

https://github.com/maxmind/libmaxminddb

Modbus library

https://libmodbus.org/

C library for creating IP packets

http://sourceforge.net/projects/libnet-dev/

HTTP/2 C Library

https://nghttp2.org/ https://github.com/nghttp2/nghttp2

HTTP/3 C Library

https://nghttp2.org/nghttp3/ https://github.com/ngtcp2/nghttp3

Implementation of QUIC protocol

https://nghttp2.org/ngtcp2/ https://github.com/ngtcp2/ngtcp2

NetSurf public suffix list handling

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

Number to number name and money text conversion libraries

https://numbertext.org

Ogg bitstream library

https://www.xiph.org/ogg/

High-level API for encoding .opus files

https://opus-codec.org/

Library to handle Apple Property List format

http://www.libimobiledevice.org

This library provides weak aliases for pthread functions

http://xcb.freedesktop.org/

Free version of the SSL/TLS protocol forked from OpenSSL

http://www.libressl.org/

TLS library designed to ease writing foolproof applications

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

Standalone port/fork of Mednafen PSX to the Libretro API

https://github.com/libretro/beetle-psx-libretro

Unofficial build of FCEU Ultra by CaH4e3

https://github.com/libretro/libretro-fceumm

Enhanced port of Genesis Plus

https://github.com/libretro/Genesis-Plus-GX

Fast MegaDrive/MegaCD/32X emulator

https://github.com/libretro/picodrive

C/C++ implementation of a Sass compiler

http://libsass.org/

Library to build higher-level cryptographic tools

https://github.com/jedisct1/libsodium

Sender Rewriting Scheme 2 C Implementation

http://www.libspf2.org/

Library to convert clothoid splines into Bezier splines

http://libspiro.sourceforge.net/

Secure RTP (SRTP) Reference Implementation

https://github.com/cisco/libsrtp

Sysctl MIB-Tree API (improved version)

https://gitlab.com/alfix/sysctlmibinfo2/

Low-level C Library to implement TLSRPT into a MTA

https://github.com/sys4/libtlsrpt

Universal configuration library parser

https://github.com/vstakhov/libucl

Implementation of the line and word breaking algorithm for Unicode

https://vimgadgets.sourceforge.net/libunibreak/

Library of Unicode annotation data

http://libuninameslist.sourceforge.net/

Generic stack unwinding library

https://github.com/libunwind/libunwind https://www.nongnu.org/libunwind/