Configuration file parsing library

http://savannah.nongnu.org/projects/confuse/

CSS2 parsing library

http://www.freespiders.org/projects/libcroco/

GNOME application for managing encryption keys (PGP, SSH)

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

Cascading Style Sheets library

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

CUE Sheet Parser Library

https://github.com/lipnitsk/libcue

Lightweight C library that eases the writing of UNIX daemons

http://0pointer.de/lennart/projects/libdaemon/

Double-array trie implementation library

https://linux.thai.net/projects/datrie/

Companion library to GObject and GTK

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

GLib and Gtk Implementation of the DBusMenu protocol

https://launchpad.net/libdbusmenu

Qt5 implementation of the DBusMenu protocol

https://launchpad.net/libdbusmenu-qt

Free DTS Coherent Acoustics decoder

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

Generic Device Query and Monitor interface

https://github.com/freebsd/libdevq

Library to generate arbitrary sequence diffs

https://github.com/kristapsdz/libdiff

Library for creating MusicBrainz DiscIDs

http://musicbrainz.org/doc/libdiscid

Reference DLNA open-source implementation

https://libdlna.geexbox.org/

Library for reading and writing Data Matrix barcodes

http://libdmtx.sourceforge.net/

DMX extension library

http://www.freedesktop.org/Software/xorg

Simple interface to low level networking routines

https://github.com/5u623l20/libdnet/

Standard library for Window Maker dock apps

http://solfertje.student.utwente.nl/~dalroi/libdockapp/

Document Object Model library

http://www.netsurf-browser.org/projects/libdom/

Userspace interface to kernel Direct Rendering Module services

https://dri.freedesktop.org/

Alsa compatibility library to build DSSI

http://www.smbolton.com/linux.html

Quasar DV codec (libdv): software codec for DV video encoding format

http://libdv.sourceforge.net/

Library for MPEG TS and DVB PSI tables decoding and generation

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

Portable abstraction library for DVD decryption

https://www.videolan.org/developers/libdvdcss.html

Videolan version of the libdvdnav project

https://www.videolan.org/developers/libdvdnav.html

MPlayer version of the libdvdread project

https://www.videolan.org/developers/libdvdnav.html

EBML (Extensible Binary Meta Language), sort of binary version of XML

https://www.matroska.org/

Collection of C++/Qt classes designed to use the APIs of The Echo Nest

https://github.com/lfranchi/libechonest

Command line editor library

http://thrysoee.dk/editline/

Public ELF file access library similar to libelf(3) in Solaris

https://web.archive.org/web/20181111033959/www.mr511.de/software/english.html

Enhanced Metafile Library

http://libemf.sourceforge.net/

Small epoll implementation using kqueue

https://github.com/jiixyj/epoll-shim

Library to handle OpenGL function pointer management

https://github.com/anholt/libepoxy

Library for generating documents in ePub format

http://libepubgen.sourceforge.net/

Liberation fonts from Red Hat to replace MS TTF fonts

https://github.com/liberationfonts/liberation-fonts

Mail framework for C language

http://www.etpan.org/libetpan.html

Full-featured and high-performance event loop library

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

Linux Event Device library

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

API for executing callback functions on events or timeouts

https://libevent.org/

Library for inspecting program's backtrace

http://www.gnu.org/software/libc/manual/html_node/Backtraces.html

Library to read digital camera file meta-data

https://libexif.github.io/

Application library for the Xfce desktop environment

https://www.xfce.org/

Language guessing by N-Gram-Based Text Categorization

https://wiki.documentfoundation.org/Libexttextcat

Video encoding library

http://fame.sourceforge.net/

Foreign Function Interface

https://sourceware.org/libffi/

Provides library functionality for FIDO 2.0

https://developers.yubico.com/libfido2/

C++ library for building platform-independent programs

https://lib.filezilla-project.org/

Core library of PCManFM file manager

https://wiki.lxde.org/en/Libfm

LibFM-Extra library

https://wiki.lxde.org/en/Libfm