ModPlug mod-like music shared libraries

https://modplug-xmms.sourceforge.net/

Perl module to manipulate filenames containing music metadata

https://erislabs.net/ianb/projects/libmp3-archive-perl/

Abstraction around libmpdclient

http://gmpc.wikia.com/

API library for interfacing MPD

https://www.musicpd.org/libs/libmpdclient/

Free library for decoding mpeg-2 and mpeg-1 video streams

http://libmpeg2.sourceforge.net/

Library for Microsoft compression formats

https://www.cabextract.org.uk/libmspack/

Multitouch Protocol Translation Library

http://bitmath.org/code/mtdev/

Media Transfer Protocol (MTP) library

https://libmtp.sourceforge.net/

MusicBrainz client library for audio metadata lookup

http://musicbrainz.org/

Brush library from the MyPaint project

http://mypaint.org/

SOFA (Spatially Oriented Format for Acoustics) file reader

https://github.com/hoene/libmysofa

NAT-PMP lightweight library

http://miniupnp.free.fr/

C library for creating IP packets

https://github.com/libnet/libnet

Client library for accessing NFS shares over a network

https://github.com/sahlberg/libnfs

HTTP/2.0 C Library

https://nghttp2.org/

Library and transmitter that implements ICE-19

https://nice.freedesktop.org

Library and transmitter that implements ICE-19

https://nice.freedesktop.org

C library, API for communicating with Creative and Dell audio players

http://libnjb.sourceforge.net/

Library for desktop notifications

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

Astronomical Calculation Library

https://libnova.sourceforge.net/

NetSurf BMP decoder

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

NetSurf GIF Decoder

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

NetSurf public suffix list handling

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

NetSurf generalised utility library

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

Library that implement Microsoft's NTLM authentication

https://www.nongnu.org/libntlm/

C library implementing the OAuth Core standard

http://liboauth.sourceforge.net/

Replacement Objective-C runtime supporting modern Objective-C features

https://github.com/gnustep/libobjc2/

OpenSource implementation of the OFX (Open Financial eXchange)

https://libofx.sourceforge.net/

Ogg bitstream library

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

Library of optimized inner loops

https://liboil.freedesktop.org/wiki/

Library which provides a way to read/write CAD (DWG/DXF/DXFB) files

https://trac.osgeo.org/gdal/wiki/DWG_driver

Module music library based on OpenMPT

https://lib.openmpt.org/

Library for camera RAW files decoding

https://libopenraw.freedesktop.org/

C++ implementation of an OpenID decentralized identity system

http://kin.klever.net/libopkele/

Library for managing OS information for virtualization

https://libosinfo.org/

Off-Screen Mesa implementation of the OpenGL API

https://www.mesa3d.org/

Library for handling OpenType fonts

https://www.nongnu.org/m17n/

Portable OTR Messaging Library and toolkit

https://otr.cypherpunks.ca/

Eclipse Paho C Client Library for the MQTT Protocol

https://github.com/eclipse/paho.mqtt.c

Library providing routines for paper size management

https://packages.qa.debian.org/libp/libpaper.html

Lexer/parser utility functions for NetSurf

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

Ubiquitous network traffic capture library

https://www.tcpdump.org/

libpcap wrapper library

https://netdude.sourceforge.net/

PCI configuration space I/O made easy

https://mj.ucw.cz/sw/pciutils/

Generic PCI access library

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

Next evolution of the Gedit plugins engine

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

Reusable library for GPU-accelerated video/image rendering

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

Library to handle Apple Property List format

https://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