Awesome

Awesome C

A curated list of C good stuff. This list contains only open source code (as defined by the linked Open Source Definition), and sellers who aren't evil for physical resources.

This is released under a Creative Commons-Attribution-ShareAlike license, version 4 (SPDX code CC-BY-SA-4.0). You can find its text in the LICENSE file.

An important note: This project does not index anything C++-related; only pure C stuff is considered.

Note for contributors: If you want to make a pull request, please read CONTRIBUTING.md first.

AI
Benchmarking
Build Systems
Compilers
Compression
Concurrency and Parallelism
Crypto
Database
Data Structures
Debugging
Documentation Generation
Editors
Embeddable Scripting Engines
Frameworks
Game Programming
Graphics
Graphical User Interface
Hashing
Learning, Reference and Tutorials
- Reference resources online
- Beginner resources online
- Intermediate resources online
- Advanced resources online
- Reference books
- Beginner books
- Intermediate books
- Advanced books
Lexing and Parsing
Memory Management
Multimedia
Networking and Internet
Numerical
Profiling
Regex
Serialization
Source Code Collections
Standard Libraries
- Template Libraries
String Manipulation
Structured File Processing
- CSV
- JSON
- INI
- Others
- XML
- YAML
Testing
Text Editor Extensions
Tools
Utilities
Web Frameworks
Windows Environments

AI

Computer vision, neural nets, machine learning, and other similar things. Basically, if your university calls it AI, it lives here.

ccv - C-based/Cached/Core Computer Vision library; modern computer vision. BSD-3-Clause
Cranium - Portable, header-only ANN library in C99. MIT
FANN - Fast Artifical Neural Network library; an implementation of neural networks. GPL-2.0-only
Genann - Simple ANN in C89, without additional dependencies. Zlib
KANN - Two-file ANN library. MIT
LibDEEP - Deep learning library. BSD-3-Clause
m2cgen - A CLI tool to transpile trained classic ML models into a native C code with zero dependencies. MIT
sod - An Embedded Computer Vision & Machine Learning Library. GPL-3.0-only

Benchmarking

Comparing the performance of various subsystems across different chip/system architectures.

b63 - Light-weight micro-benchmarking tool for C. Apache-2.0

Build Systems

Tools that automate the building and testing of projects in C.

Autotools - Also known as the GNU build system (automake, autoconf, libtool...) is one of the most widely used build systems (configure && make). GPL-1.0-or-later
Autotools project skeleton - A simple autotools skeleton (template) to quickly bootstrap new projects. BSD-2-Clause
CMake - Cross-platform family of tools designed to build, package and test software. BSD-3-Clause
GNU Make - Tool which controls the generation of executables and other non-source files of a program. GPL-3.0-or-later
Meson - Extremely fast, user-friendly build system. Based on Ninja. Apache-2.0
Premake - Command-line utility which reads a scripted definition of a software project and uses it to generate project files for Visual Studio and GNU Make. Other targets are also being worked on. BSD-3-Clause
SCons - Software construction tool using Python. MIT
xmake - Cross-platform build utility. Apache-2.0
zproject - Project generator and build system support tool. MPL-2.0

Compilers

Compilers, as well as compiler- and compilation-related tooling.

ccache - Compiler cache designed to speed up recompilation. GPL-3.0-or-later
Clang - Compiler for LLVM. Supports C11. NCSA
cproc - A C11 compiler using QBE as a backend. ISC
distcc - Program that allows builds to be distributed among several machines. GPL-2.0-or-later
Firm - Library that provides a graph-based intermediate representation, optimizations and assembly code generation suitable for use in compilers. Comes with an example C front-end under the same license. LGPL-2.1-only
GCC - Provides a C compiler as part of its compiler set. Supports C11. GPL-3.0-or-later
PCC - Venerable compiler. Supports C99. Various licenses, all open source.

Compression

blosc - Extremely fast, multi-threaded, meta-compressor library. Various licenses, all open source.
Brotli - General-purpose lossless compression algorithm library. Has speeds comparable to DEFLATE, but much higher compression ratios. MIT.
clzip - C version of the high-quality data compressor Lzip (LZMA implementation). GPL-2.0-or-later
CRoaring - C implementation of Roaring bitmaps. Apache-2.0
FiniteStateEntropy - Two highly efficient compression codecs optimized for modern CPUs. BSD-2-Clause
DENSITY - Super-fast compression library. BSD-3-Clause
heatshrink - Data compression/decompression library for embedded and real-time systems. ISC
fast_zlib - Improved zlib, which runs 2 to 10 times faster. BSD-3-Clause
fastLZ - Lightning-fast lossless compression library (LZ77 type). Embbedable on small target like ARM Cortex-M families. Source code directly embbedable on your project ( a pair of h/c files), no dynamic memory allocation. MIT
huffandpuff - Minimal Huffman encoder and decoder. Public domain.
libzip - C library for reading, creating and modifying zip archives. BSD-3-Clause
libbzip2 - Patent-free, high-quality data compression library. BSD-4-Clause
Lizard - Formerly LZ5; an efficient compressor with fast decompression. Achieves compression ratios comparable with zip and zlib at decompression speeds of 1000MB/s and faster. BSD-2-Clause
lz4 - Library for an extremely fast compression algorithm. BSD-2-Clause
lzo - Fast data compression library. GPL-2.0-or-later
pixz - Parallel, indexed xz compressor. BSD-2-Clause
shoco - Compressor for small text strings. MIT
SIMDComp - Simple library for compressing lists of integers using binary packing. Makes use of SIMD instructions on x86. BSD-3-Clause
smaz - Efficient string compression library. BSD-3-Clause
squash - Compression abstraction library, complete with some utilities. MIT
TurboPFor - Fastest integer compression. GPL-2.0-or-later
TurboRLE - Most efficient run-length encoding. GPL-2.0-or-later
zip - Really really small zip archive processing library. Unlicense
Zlib - Massively spiffy yet delicately unobtrusive compression library. BSD-3-Clause
libarchive - libarchive is a portable, efficient C library that can read and write streaming archives in a variety of formats. BSD-3-Clause
zlib-ng - Zlib replacement with optimizations for 'next-generation' systems. BSD-3-Clause
Zstandard - Fast, lossless compression algorithm, targeting real-time compression scenarios at zlib-level or better compression ratios. BSD-3-Clause

Concurrency and Parallelism

cchan - Small library for channel constructs for inter-thread communication. Public domain.
checkedthreads - A simple library for parallelism, with built-in checking for race conditions. BSD-2-Clause
ck - Concurrency primitives, safe memory reclamation mechanisms and non-blocking data structures. BSD-2-Clause
FCFS RWLock - First-come first-served Readers/Writers lock for POSIX threads. CC0-1.0
Libaco - A blazing fast and lightweight C asymmetric coroutine library. Apache-2.0
libconcurrent - Concurrent programming library, using coroutines, for C11. BSD-3-Clause
libcsp - High performance concurrency C library influenced by the CSP model. MIT
libdill - Library which makes structured concurrent programming easy. MIT
libhl - Library implementing a thread-safe API to manage a range of data structures. Also provides some supporting functions and structures for concurrent and lockfree programming. LGPL-3.0-only
liburcu - Data synchronization library, which scales linearly with the number of cores. LGPL-2.1-or-later
mill - Go-style concurrency. MIT
oclkit - Two-file OpenCL wrapper. GPL-3.0-or-later
OCL-MLA - OpenCL Mid-Level Abstractions. BSD-3-Clause
OpenMP - Set of pragmas designed to allow for easy parallelization of code. Standard (licensing not applicable).
Open MPI - Message passing interface implementation. BSD-3-Clause
pal - Optimized library for maths, parallel processing and data movement. Apache-2.0
pth - Portable implementation for non-preemptive priority-based scheduling for multiple threads of execution. GPL-3.0-or-later
pthreads - POSIX thread library. Standard (no license applicable).
TinyCThread - Portable, small implementation of the C11 threads API. Zlib

Crypto

Mostly library implementations of well-known cryptographic algorithms or protocols.

GNU SASL - Implementation of the Simple Authentication and Security Layer and a few common SASL mechanism. GPL-3.0-or-later
GnuTLS - Secure communication library, implementing SSL, TLS and DTLS. LGPL-2.1-or-later
libgcrypt - General-purpose cryptography library, with a range of available ciphers. LGPL-2.1-or-later
OpenSSL - Implementation of the SSL and TLS protocols. Also includes a cryptography library. Dual Licensed under the OpenSSL License and the SSLeay License.
liboqs - Library for quantum-resistant cryptographicl algorithms. MIT
libsodium - Modern and easy-to-use crypto library. MIT
libtomcrypt - Fairly comprehensive, modular and portable cryptographic toolkit. Public domain.
mbed TLS - Another crypto implementation. Apache-2.0
MIRACL - Multiprecision Integer and Rational Arithmetic Cryptographic Library; an SDK for elliptic curve cryptography. AGPL-3.0-or-later
retter - Collection of hash functions, ciphers, tools, libraries and materials related to cryptography and security. Public domain.
s2n - C99 implementation of the TLS/SSL protocols, designed to be simple, fast and with security as a priority. Apache-2.0
sphlib - Set of implementations of various hash functions, including several cryptographic ones. MIT
trezor-crypto - Heavily optimized crypto algorithms for embedded devices. MIT
bfish - A single include ANSI-C Blowfish ECB crypto library. Public domain.

Database

Databases and data stores with C APIs.

BerkeleyDB - Library for a high-performance embedded database for key-value data. AGPL-3.0-only
DuckDB - Fast in-process analytical database, with C API. MIT
EJDB2 - Embeddable JSON Database engine. MIT
Groonga - Columnar store with full-text search. LGPL-2.1-only
Hiredis - Minimalistic client library for Redis. BSD-3-Clause
libmongoc - High-performance client library for MongoDB. Apache-2.0
LMDB - Ultra-fast, ultra-compact key-value embedded data store. OLDAP-2.8
MySQL - The world's most popular open source database. GPL-2.0-only
PostgreSQL - Powerful object-relational database system. PostgreSQL
Redis - Advanced key-value store. BSD-3-Clause
sophia - Modern, embeddable key-value database. BSD-2-Clause
sparkey - Simple constant key/value storage library. Designed for read-heavy loads with infrequent, large bulk inserts. Apache-2.0
SQLite - Self-contained, serverless, zero-configuration, transactional SQL database engine. Public domain.
UnQLite - Self-contained, serverless, zero-configuration, transactional NoSQL engine. BSD-2-Clause
WhiteDB - Lightweight database library, operating entirely in main memory. GPL-3.0-or-later
FlashDB - An ultra-lightweight database that supports key-value and time series data. Apache-2.0
TDengine - High-performance, cloud native time-series database. AGPL-3.0-only

Data Structures

C-Macro-Collections - Generate simple and generic data structures using macros. MIT
CLIST - Simple and lightweight dynamic array implementation. BSD-2-Clause
Collections-C - Library of generic data structures. LGPL-3.0-or-later
ds - Common Data Structures and Algorithms. MIT
igraph - A graph processing library. GPL-2.0-or-later
kdtree - Simple library for working with KD-trees. BSD-3-Clause
libavl - Library containing a range of self-balancing binary trees. GPL-3.0-or-later
libcdada - A small, portable, MACRO-less library for basic data structures (list, set, map, queue...) in C (C++ backend). BSD-2-Clause
liblfds - Portable lock-free data structure library. Public domain (more exactly, whatever license you want).
libsrt - Soft and hard real-time data structures. BSD-3-Clause.
list.h - Implementations for singly linked and doubly linked list functions. GPL-3.0-only
M*LIB - Library for generic, but typesafe C containers. Implemented as header-only. BSD-2-Clause
offbrand - Collection of generic, reference-counted data structures. MIT
PackedArray - Random-access array of tightly packed unsigned integers of any desired width. Has a SIMD-optimized implementation. WTFPL
rb3ptr - Red-Black tree. Exposes almost all implementation primitives, so can be used for scenarios like augmentation, multiple compatible ordering functions, and more. MIT
uthash - Single-file hash table implementation. BSD-1-Clause
vector.h - Header library for typed lists. MIT

Debugging

Because we all have to do it sometimes. Various tools for making debugging easier or better, as well as libraries or code that allows better debugging work.

C-Reduce - Tool that takes a large C file with a property of interest and automatically produces a much smaller C file that has the same property. Intended to help create minimal bug-demonstrating cases in complex code. BSD-3-Clause
CBMC - C Bounded Model Checker; a tool for verification of array bounds, pointer safety and user-specified assertions. BSD-4-Clause
cflow - Analyzes a collection of source files and prints a graph charting control flow in the program. GPL-3.0-or-later
Complexity - Tool for measuring the complexity of source code. GPL-3.0-or-later
CScout - Source code analyzer and refactoring browser for C programs. GPL-3.0-only
DDD - Graphical front-end for a range of command-line debuggers. GPL-3.0-or-later
debug - One-header library for easier 'printf debugging'. MIT
ESBMC - Efficient SMT-based Bounded Model Checker; a tool for verification of single and multithread programs, user assertions, overflow, and pointer/memory safety. Apache-2.0
GDB - GNU Project debugger. GPL-3.0-or-later
lldb - LLVM debugger. NCSA
rr - Debugger that records non-deterministic executions to allow for deterministic debugging. BSD-2-Clause
Valgrind - Range of dynamic analysis tools, including a leak checker. GPL-2.0-only

Documentation Generation

Cxref - Generates documentation in either LaTeX, HTML, RTF or SGML. GPL-2.0-only
DocOnce - Modestly tagged markup language that can be used to generate a range of formats. BSD-3-Clause
Doxygen - De-facto standard tool for generating documentation from annotated sources. Can generate a large range of formats. GPL-2.0-only

Editors

Fancier, IDE-type editors. If you want a programmer's text editor, look elsewhere. Besides, whatever you use most likely supports C anyway.

Anjuta DevStudio - GNOME IDE. GPL-2.0-only
Code::Blocks - Extendable, configurable IDE supporting C. GPL-3.0-only
CodeLite - Cross-platform IDE. GPL-2.0-only
Geany - Small and fast IDE. GPL-2.0-or-later
KDevelop - KDE IDE. GPL-2.0-only
zinjaI - Simple, lightweight and feature-rich IDE. GPL-3.0-only

Embeddable Scripting Engines

When C isn't the right solution, or when you need a more dynamic configration engine:

Duktape - Embeddable Javascript engine with a focus on portability and compact footprint MIT.
MetaCall - Cross-platform Polyglot Runtime which supports NodeJS, JavaScript, TypeScript, Python, Ruby, C#, Wasm, Java, Cobol and more. Apache-2.0

Frameworks

Big libraries that provide data structures and other stuff you expect of a 'modern' standard library.

APR - Apache Portable Runtime; another library of cross-platform utility functions. Apache-2.0
C Algorithms - Collection of common algorithms and data structures. ISC
CPL - The Common Pipeline Library; a set of libraries designed to be a comprehensive, efficient and robust software toolkit. GPL-2.0-only
EFL - Large collection of useful data structures and functions. Various licenses, all open source.
GLib - Library of utility functions and structures, designed to be portable, efficient and powerful. LGPL-2.1-only
klib - Small and lightweight implementations of common algorithms and data structures. MIT
libcork - Utility functions and structures, designed for resource-constrained systems. Can be embedded. BSD-3-Clause
libnih - Lightweight library of functions and structures. GPL-2.0-only
libU - Small library of basic utilities, including memory allocation, string manipulation and logging. BSD-3-Clause
PBL - Large library of utilities, featuring data structures, among other things. LGPL-2.1-or-later
plibsys - Cross-platform system C library. Zero third-party dependencies, uses only native system calls. MIT
qlibc - Simple and powerful library, designed as a replacement for GLib while focusing on being small and light. BSD-2-Clause
sc - Common libraries and data structures for C. MIT
TBOX - Multi-platform library with a large number of capabilities. Apache-2.0
pspsdk - An open-source SDK for PSP homebrew development. Various licences.

Game Programming

Engines, libraries and other helpful things specifically for making games.

Allegro - Cross-platform, video game development and multimedia library. Zlib
AssetKit 🎨 3D asset importer/exporter/util library based on COLLADA/glTF specs MIT
astera - C99 Cross Platform 2D Game Library MIT
cglm - 📽 Optimized OpenGL/Graphics Math (glm) for C. MIT
Chipmunk2D - Fast and lightweight 2D game physics library. MIT
cmt - 🎮 C Bindings/Wrappers for Apple's METAL Graphics Framework. MIT
Corange - Game engine in pure C. BSD-2-Clause
CSFML - Binding for SFML. Zlib
Darkplaces - Modified version of the Quake2 engine. GPL-2.0-only
Epoxy - Library for handling OpenGL function pointer management. MIT
exengine - 3D game engine in C99 with a starting template. MIT
Flecs - A Multithreaded Entity Component System written for C89 & C99 MIT
Freecell Solver - Set of libraries and command-line programs for automatically solving FreeCell and some similar variants of card Solitaire. MIT
FreeGLUT - Alternative to the OpenGL Utility Toolkit. Allows the creation and management of windows with OpenGL contexts. X11
GLFW - Multi-platform library for creating windows with OpenGL contexts. Zlib
ioquake3 - Quake3 engine, freed at last. GPL-2.0-only
kazmath - Maths library for games. BSD-2-Clause
libao - Cross-platform audio library with a wide variety of outputs. GPL-2.0-or-later
librg - Pure C99 game networking library for building simple and elegant cross-platform multiplayer client-server solutions. Apache-2.0
MATHC - Math library for 2D and 3D programming. ZLib
Orx - Portable, lightweight, plugin-based, data-driven, 2D-oriented game engine. Zlib
Quake - Quake engine. GPL-2.0-only
Quake2 - Quake2 engine. GPL-2.0-only
raylib - Simple and easy-to-use library to learn video game programming. Zlib
RetroArch - Reference frontend for libretro. GPL-3.0-only
SDL2 - Cross-platform library designed to provide low-level access to audio, keyboard, mouse, joystick and graphics hardware via OpenGL. Zlib
sdl-gpu - Library for high-performance, modern 2D graphics. Based on SDL. MIT
SIGIL - Sound, Input and Graphics Integration Library; a simple alternative to other libraries for doing all those things. Various licenses, all open source.
uastar - Minimal A* implementation. ZLib

Graphics

Programmatic manipulation of graphics in C; if you want to make a GUI, the Graphical User Interface section has what you need.

AssetKit 🎨 3D asset importer/exporter/util library based on COLLADA/glTF specs MIT
Cairo - 2D graphics library. LGPL-2.1-only or MPL-1.1.
cmt - 🎮 C Bindings/Wrappers for Apple's METAL Graphics Framework. MIT
giflib - Library for reading and writing gif images. MIT
graphene - Thin layer of graphical data types. MIT
heman - Tiny library of image utilities dealing with height maps, normal maps, distance fields and the like. MIT
libcaca - ASCII renderer for terminal-based interfaces. WTFPL
libgd - Library for the dynamic creation of images by programmers. MIT
libimagequant - Small, portable library for high-quality conversion of RGBA images to 8-bit indexed colour images. GPL-3.0-or-later
libjpeg-turbo - Faster library for reading and writing JPEG files. Various licences.
libpng - Official PNG reference library. Libpng
libRSVG - Library to render SVG files using Cairo. LGPL-2.1-or-later
libsixel - Library implementing the SIXEL protocol, allowing beautiful graphics in your terminal. MIT
libspng - A simpler interface for reading and writing PNG files. BSD-2-Clause
libvips - Image processing library. LGPL-2.1-or-later
libxmi - Function library for rasterizing 2D vector graphics. GPL-3.0-or-later
lightmapper - Single-file library for lightmap baking, using an existing OpenGL renderer. Public domain.
little CMS - A Color Management System. It provides fast transforms between ICC profiles. MIT
mozjpeg - Improved JPEG encoder. BSD-3-Clause
nanovg - Anti-aliased 2D vector drawing library on top of OpenGL, for UI and visualizations. Zlib
OpenGL - Industry standard for high-performance graphics, with a native C binding. Various licenses.
PlutoVG - A standalone 2D vector graphics library in C MIT
SAIL - ⛵ The missing small and fast image decoding library for humans (not for machines) MIT

Graphical User Interface

Widget toolkits, or things meant to be used in a similar way to them.

GTK+ - Cross-platform widget toolkit. LGPL-2.1-only
IUP - Another cross-platform widget toolkit. MIT
microui - Tiny immediate-mode UI library written in portable ANSI C. MIT
nappgui - Professional SDK to build cross-platform desktop applications using C. MIT
nuklear - Small, C89, single-header widget toolkit. Public domain.
tinyfiledialogs - Single-file library for simple dialogs. Compatible with many other toolkits and OSes. Zlib
Tk - Basic widget toolkit. Part of Tcl/Tk. TCL
XForms Toolkit - Widget toolkit designed for the XWindow system. LGPL-2.1-only
LVGL - embedded GUI with easy-to-use graphical elements, beautiful visuals and a low memory footprint. MIT
luigi - A barebones single-header GUI library for Win32, X11 and Essence. MIT

Hashing

Hash function implementations for non-crypto purposes. Cryptographic hashes can be found in the Crypto section.

CLHash - Library implementing the ridiculously fast CLHash hashing function. Only works on Intel Haswell or newer. Apache-2.0
HighwayHash - Fast, strong, SIMD-using hash function. Also contains an implementation of SipHash (although this is slower). Apache-2.0
SpookyHash - Extremely fast hash function. BSD-3-Clause
t1ha - Fast Positive Hash - a portable, fast hash function. BSD-3-Clause
xxHash - Extremely fast hashing algorithm. Comes in 32 and 64-bit varieties. BSD-2-Clause

Learning, Reference and Tutorials

Resources for learning C programming in general, or something useful relating to C programming.

Reference resources online

Benchmarks of the Lockless Memory Allocator
C FAQ - comp.lang.c Frequently Asked Questions
Comparison of C/POSIX standard library implementations for Linux
Draft C89 standard
Draft C99 standard
Draft C11 standard
Finding the best 64-bit simulation PRNG
SEI CERT C Coding Standard
tinyc.game - Tiny C games you can compile and run RIGHT NOW http://tinyc.games MIT

Beginner resources online

A tutorial on pointers
A tutorial on portable Makefiles
Building C Projects
C Programming Wikibook
Introduction to `fun' C
Learning C with GDB
memcpy vs memmove
POSIX Threads Programming tutorial (a little dated, but most of it is still valid and useful)
The GNU C Programming Tutorial (online PDF)
Templating in C
What a C programmer should know about memory
CodeforWin: Learn C Programming, Data Structures Tutorials and Exercises online
Learn C: Free and Open-Source Interactive C Tutorial
How to program a text adventure in C

Intermediate resources online

Advanced resources online

Reference books

C: A Reference Manual 5E - Full reference book for C99.
C in a Nutshell 2E - Concise reference book for C11.
C Pocket Reference - Concise reference book for C99.
The C Programming Language 2E - Original book on C, by its creators.

Beginner books

C Primer Plus 6E - Complete tutorial on programming in C11.
C Programming: A Modern Approach - Excellent book to learn the basics of C.
Head First C - 'Head-first' style book for learning C.

Intermediate books

21st Century C - Good second programming book on C.
Understanding and Using C Pointers - In-depth resource on pointers in C.
ZeroMQ - Book for using ZeroMQ with C.

Advanced books

Expert C Programming: Deep C Secrets - Interesting, in-depth and entertaining look at the innards of C.
Modern C, Third Edition: Covers the C23 standard - In Modern C, Third Edition you’ll learn to harness C’s full potential using the latest tools and techniques.

Lexing and Parsing

Libraries specifically for lexical analysis (or lexing) and syntactic analysis (or parsing).

flex - Fast lexical analyzer generator. BSD-2-Clause
GNU Bison - General-purpose parser generator that converts an annotated context-free grammar into a range of parsers. GPL-3.0-or-later
hammer - Parser combinators for binary formats. GPL-2.0-only
mpc - Parser combinator library. BSD-2-Clause
owl - A parser generator for visibly pushdown languages. MIT
re2c - Lexer generator, producing fast lexers, with access to its internals. Public domain.

Memory Management

Whether a different, faster malloc or outright garbage collection, anything to do with managing C memory lives here.

Boehm GC - Garbage collection for C. Various licenses, all open source.
jemalloc - Malloc implementation that emphasizes avoidance of fragmentation and scalable concurrency support. BSD-2-Clause
Lockless Memory Allocator - Efficient memory allocator. GPL-3.0-or-later
libcsptr - Smart pointers for C. MIT
rpmalloc - Thread-caching, fast memory allocator, naturally aligned on 32-byte boundaries. Public domain.
talloc - Hierarchical, reference-counted memory pool system with destructors. LGPL-3.0-or-later
tlsf - Two-Level Segregated Fit allocator; a general-purpose, dynamic memory allocator designed to meet real-time requirements. Up-to-date implementation. BSD-3-Clause

Multimedia

aubio - Library for audio and music analysis. GPL-3.0-or-later
FFMPEG - Complete, cross-platform solution to record, convert and stream audio and video. LGPL-2.1-or-later
GStreamer - Framework for audio and visual media. LGPL-2.1-or-later
libmpv - Music-playing library. GPL-2.0-or-later
libsndfile - Library for reading and writing sound files. Supports many formats. LGPL-2.1-only or LGPL-3.0-only
libsoundio - Library for cross-platform, real-time audio input and output. Has a range of back-ends. MIT
libVLC - Complete multimedia library for audio and video encoding, decoding, playing and streaming. GPL-2.0-only
lodepng - Simple PNG image decoder and encoder, requiring no other dependencies. BSD-3-Clause
minimp3 - Lightweight MP3 decoder single header library. CC0-1.0
Soundpipe - Lightweight music DSP library. MIT

Networking and Internet

Low-level networking and internet-related stuff. If you want something more comprehensive and high-level, you may want the Web Frameworks section.

asnlc - Compiler of ASN.1 specifications into C source code. BSD-2-Clause
CHL - C Hypertext Library - A library for writing web applications in C. GPL-3.0-only
czmq - High-level binding for ZeroMQ. MPL-2.0
Dyad.c - Lightweight, easy, asynchronous networking library. MIT
GNU adns - Advanced, easy-to-use, asynch-capable DNS client library and utilities. GPL-3.0-or-later
gumbo-parser - HTML5 parsing library in C99. Apache-2.0
H20 - A new-generation HTTP server. MIT
llhttp - HTTP request/response parser. MIT
ldns - Library to simplify DNS programming. BSD-3-Clause
libcurl - Client-side URL transfer library, supporting a wide range of formats. curl
LibEtPan - Mail library providing an efficient network for IMAP, SMTP, POP and NNTP. BSD-3-Clause
libev - Yet another event loop. BSD-2-Clause
libevent - Event loop replacement for network servers. BSD-3-Clause
libhttpd - Library to add basic web server capabilities to an application or embedded device. GPL-2.0-only
libhv - Cross platform event loop library. BSD-3-Clause
libidn - Implementation of the Stringprep, Punycode and IDNA specifications. GPL-3.0-or-later
libmicrohttpd - Small library that makes it easy to run an HTTP server as part of another application. LGPL-2.1-or-later
libnl - libnl is a collection of libraries to provie APIs to the Netlink protocol (replacement for ioctl). It's primary use is to communicate with the Linux kernel, to modify networking state (interfaces, routing etc...). LGPL-2.1-only
libonion - HTTP server library, designed to be easy to use. Apache-2.0
libpcap - API provides to various kernel packet capture mechanism. BSD-3-Clause
libquickmail - Library intended to give developers a way to send email from their applications. Supports multiple To/Cc/Bcc recipients and attachments without size limits. GPL-3.0-or-later
libsagui - Library for cross-platform HTTP servers. LGPL-3.0-or-later
libuhttpd - A very flexible, lightweight and fully asynchronous HTTP server library based on libev and http-parser for Embedded Linux. MIT
LibVNCServer - Cross-platform libraries to implement VNC server and/or client functionality. GPL-2.0-or-later
libwebsock - Easy-to-use and powerful web socket library. LGPL-3.0-only
libzmq - Core ZeroMQ library, a high-performance asynchronous messaging library, aimed at use in distributed or concurrent applications. C API (backend C++) GPL-3.0-or-later with static linking exception
lwan - Experimental, scalable, high-performance HTTP server. GPL-2.0-only
mongoose - Embedded web server. GPL-2.0-only
MQTT-C - A portable MQTT C client for embedded systems and PCs alike. MIT
nanomsg - C-based implementation of ZeroMQ. MIT
NNG - nanomsg-next-generation - lightweight brokerless messaging. MIT
oSip - SIP implementation without additional dependencies. LGPL-2.1-or-later
silgy - Asynchronous HTTP(S) engine for C/C++ projects. MIT
socket99 - C99 wrapper for the BSD sockets API. ISC
twitc - Mini library for interacting with the Twitter OAuth API. MIT
uriparser - Strictly RFC 3986-compliant URI parsing and handling library. BSD-3-Clause
Wslay - WebSocket library. Implements version 13 of the WebSocket protocol, as described in RFC 6455. MIT
zyre - Framework for proximity-based peer-to-peer applications. MPL-2.0

Numerical

apophenia - Library for statistical and scientific computing. GPL-2.0-only
Arb - Library for arbitrary-precision interval arithmetic. LGPL-2.1-or-later
ATLAS - Automatically Tuned Linear Algebra Software. BSD-3-Clause
clBLAS - BLAS functions written in OpenCL. Apache-2.0
cmathl - Math library with a great variety of mathematical functions with CMake build support. Seeks to be close to C89/C90 compliant for portability. MIT
Cuba - Library for multidimensional numerical integration. LGPL-3.0-only
fft-c - A high-performance Fourier Transform from netlib's fftpack; wrapped in a user-friendly format MIT
FFTW - The Fastest Fourier Transform in the West; a highly optimized fast Fourier transform routine. GPL-2.0-or-later
FLINT - Fast Library for Number Theory; a library supporting arithmetic with numbers, polynomials, power series and matrices, among others. GPL-2.0-or-later
GLPK - GNU Linear Programming Kit; a package designed for solving large-scale linear programming, mixed integer programming and other related problems. GPL-3.0-or-later
GMP - GNU Multple Precision Arithmetic Library; a library for arbitrary-precision arithmetic. GPL-2.0-only or LGPL-3.0-only
GNU MPC - Library for complex number arithmetic. LGPL-3.0-or-later
GNU MPFR - Library for arbitrary-precision floating-point arithmetic. LGPL-3.0-or-later
GNU MPRIA - Portable mathematics library for multi-precision rational interval arithmetic. GPL-3.0-or-later
GSL - The GNU Scientific Library; a sophisticated numerical library. GPL-3.0-only.
KISS FFT - Simple fast Fourier transform library. BSD-3-Clause
LAPACKE - Interface to LAPACK. BSD-3-Clause
LibTomMath - Portable, number-theoretic, multiple-precision integer library. Supports algebra, digit manipulation, modular reductions, and various number-theoretic routines. Public domain.
LibTomPoly - Polynomial-related maths library. Public domain.
PARI/GP - Computer algebra system for number theory; includes a compiler to C. GPL-2.0-or-later
PETSc - Suite of data structures and routines for scalable parallel solution of scientific applications modelled by partial differential equations. BSD-2-Clause
SCS - Splitting Conic Solver; a numerical optimization package for solving large-scale convex cone problems. MIT
SLEPc - Library for the solution of large, sparse eigenvalue problems on parallel computers. LGPL-3.0-only
TomsFastMath - Set of optimized maths operations (in assembly), suitable for cryptographic use. Public domain.
Yeppp! - Fast, SIMD-optimized mathematical library. BSD-3-Clause

Profiling

gperftools - Collection of utilities for measuring and improving performance. BSD-3-Clause
gprof - Performance analysis tool. Part of GNU binutils. GPL-3.0-or-later
OProfile - Statistical profiler for Linux. Can profile any code (including the kernel!) with low overhead and without recompilation. GPL-2.0-only
perf - Linux kernel-based profiler with a lot of functionality. GPL-2.0-only

PDF

pdfio - PDFio is a simple C library for reading and writing PDF files.Apache-2.0

Regex

Onigmo - Fork of Oniguruma, supporting more advanced regexps. BSD-2-Clause
Oniguruma - Regex library supporting a wide range of encodings, and incorporating many security-oriented fixes. BSD-2-Clause
PCRE - Implementation of regexes identical to that of Perl 5. BSD-3-Clause
SLRE - Super Light Regular Expression library; a small implementation of a subset of Perl regex syntax. GPL-2.0-only
TRE - POSIX-compliant, feature-full regex library. BSD-2-Clause

Serialization

binn - Binary serialization format, meant to be compact, fast and easy-to-use. Apache-2.0
c-capnproto - Implementation of the Cap'n Proto serialization protocol. MIT
cmp - Implementation of the MessagePack serialization protocol. MIT
flatcc - FlatBuffers compiler and library. Apache-2.0
libavro - Implementation of the Avro data serialization system. Apache-2.0
mpack - Another implementation of the MessagePack serialization protocol. MIT
OPIC - Object Persistence in C; a revolutionary serialization framework, with matching on-disk and in-memory representations. GPL-3.0-or-later
protobuf-c - Implementation of Google Protocol Buffer. BSD-2-Clause
tpl - Small binary serialization library. MIT
xdr - External Data Representation; a standard for data serialization. Standard (no license applicable).
pbtools - Google Protocol Buffers C source code generator. MIT

Source Code Collections

Collections of small source code. If you want something big and integrated, check the Frameworks section.

CCAN - Modelled after Perl's CPAN, this is a big collection of code that does stuff. The full list is here. Various licenses, all open source.
clib - Something of a package manager. Comes with a bunch of libraries of its own. MIT
gnulib - Collection of common GNU code. Various licenses, all open source.
libdjb - Collection of libraries doing various things. (Apparently) public domain.
mmx - Collection of single-header libraries. Various licenses, all open source.
par - Bunch of single-file libraries. MIT
Snippets - Useful code snippets and header-only libraries. Public domain.
stb - Range of single-file libraries. Public domain.
tinyheaders - Collection of header-only libraries, primarily oriented toward game development. Zlib
zpl - C99 cross-platform header-only library with many goodies. [BSD-3-Clause, Unlicense][BSD-3-Clause, Unlicense]

Standard Libraries

Implementations of the (standard-mandated) C standard library.

Bionic - Google's standard library, developed for Android. BSD-3-Clause
cloudlibc - Standard library based on the concept of capability-based security. BSD-2-Clause
dietlibc - Standard library designed for the smallest possible binaries. GPL-2.0-only
glibc - The GNU C Library; an implementation of the standard library. LGPL-2.1-only.
musl - Standard library, compatible with POSIX 2008 and C11. Designed for static linking. MIT
PDCLib - The Public Domain C Library. Implements most of C99 and some of C11. CC0-1.0
uClibc-ng - Small C library for developing embedded systems. LGPL-2.1-or-later

Template libraries

CTL - C CONTAINER TEMPLATE LIBRARY (CTL) MIT

String Manipulation

bstring - The Better String Library. BSD-3-Clause
ICU - International Components for Unicode; a library for Unicode support. ICU
levenstein.c - Levenstein distance algorithm implementation. MIT.
libunistring - Library for manipulating Unicode strings. LGPL-3.0-only
libgiconv - Text conversion library. LGPL-2.1-only
librope - UTF-8 rope ('heavy' string) library. MIT
SDS - Simple Dynamic Strings; a library for handling strings in a simpler way, but one that is compatible with normal C string functions. Available via clib. BSD-2-Clause
stmr.c - Porter Stemmer algorithm implementation. MIT
str - Yet another string library for C language. BSD-3-Clause
StringZilla - Up to 10x faster SIMD and SWAR-accelerated string search, sort, hashes, edit distances, alignments, and generators. Apache-2.0
utf8.h - Single-header UTF-8 library, designed to mimic C-style string functions. Public domain.
utf8proc - Library for processing UTF-8 data. MIT

Structured File Processing

This includes libraries for things like XML, JSON, CSV, and other similar formats.

CSV

libcsv - Simple, streaming CSV parser. LGPL-2.1-or-later

JSON

Jansson - Library for encoding, decoding and manipulating JSON. MIT
jfes - JSON For Embedded Systems; simple JSON engine without any dependencies. MIT
jsmn - Minimalistic JSON parser. MIT
json - Simple, low-memory-use JSON parser. MIT
json-c - Easily work with JSON in C. Comes with a reference-counted object model, and aims for conformance with RFC 7159. MIT
json.h - Single-file non-streaming JSON parser. Unlicense
parson - Two-file, C89-compatible JSON parser. MIT
WJElement - Advanced JSON manipulation library, with support for JSON Schema. LGPL-2.0-or-later or LGPL-2.1-or-later or LGPL-3.0-or-later
YAJL - Fast streaming JSON parser library. ISC

INI

inih - Small and simple INI file parser, good for embedded systems. BSD-3-Clause
iniparser - Parser for .ini files. MIT
libconfini - Yet another INI parser. GPL-3.0-only
minIni - Small and portable INI parser. Apache-2.0

Others

libbson - BSON utility library. Apache-2.0
libcbor: CBOR protocol implementation for C and others. MIT
libconfuse - Small configuration file parser library. ISC
libelf - Simple library for parsing ELF files. MIT
libucl - Universal configuration library parser. BSD-2-Clause
libxo - Allows an application to generate plain text, XML, JSON and HTML output using a common set of function calls. The application decides at runtime what output style should be produced. BSD-2-Clause

XML

Expat - Stream-oriented XML parser. MIT
libxml2 - Standards-compliant, portable XML parser. MIT
xml - Simple, low-memory-use XML parser / tokenizer. MIT

YAML

libYAML - YAML 1.1 parser and emitter. MIT

Signal Processing

libsigrok - signal analysis software suite that supports various device types (such as logic analyzers, oscilloscopes, multimeters, and more). [GPL][GPL]

Testing

CHEAT - Simple unit testing framework. BSD-2-Clause
Check - Unit testing framework. LGPL-2.1-only
ciut - A modern minimal hassle unit test framework. MIT
clar - Clear and simple unit testing framework. MIT
CMock - Mock/stub generator. MIT
cmocka - Unit testing framework with support for mock objects. Apache-2.0
Criterion - KISS, non-intrusive test framework. MIT
ctest - Yet another unit testing framework. Apache-2.0
CUnit - Another unit testing framework. LGPL-2.1-or-later
greatest - Unit testing library in one file, with no memory allocation. ISC
minctest - Unit testing microlibrary. BSD-3-Clause
munit - Small unit testing framework. MIT
Nala - A test framework for C projects. MIT
Rexo - Framework for C89/C++ featuring automatic registration of tests and a polished API. Unlicense
Tau - A Micro Unit testing framework for C/C++ (~1k lines of code). Includes a rich set of assertion macros, supports automatic test registration and can output to multiple formats, like the TAP format or JUnit XML. Supported on Linux, macOS, FreeBSD, and Windows. MIT
theft - Property-based testing (similar to Quickcheck). MIT
Unity - Simple unit testing framework. MIT
utest - Single-header unit testing library. Unlicense

Text Editor Extensions

While practically any decent programmer's text editor supports C, there are some extensions that make it more pleasant. These are labelled by editor.

CCompletion - Notepad++ autocompletion plugin. Works with all identifiers recognized by Ctags. This is a download link. GPL-2.0-or-later
CEDET - Collection of Emacs Development Environment Tools; designed to provide IDE-like features to Emacs. Built-in. GPL-3.0-or-later
Flycheck - Modern syntax checking for Emacs. For C, it can use either GCC or Clang as a back-end. GPL-3.0-or-later
Neomake - Async :make and linting framework for Neovim/Vim. MIT
Syntastic - Syntax checking and linting for Vim. WTFPL
YASnippet - Emacs code template system, with C templates for common snippets. GPL-3.0-or-later
YouCompleteMe - Code completion engine for Vim. GPL-3.0-only

Tools

Useful programs to help you write and debug C code which are not editors, libraries or compilers.

Artistic Style - Fast and small automatic source code formatter that supports C. LGPL-3.0-only
address-sanitizer - Fast memory error detector. Apache-2.0
bcc - A byte array generator to import binary files directy from C in the spirit of xxd. ISC
c - Compile and execute C "scripts" in one go on the command line. Also has shebang support. MIT
c99sh - Run C files using hash-bang. BSD-2-Clause
cdecl - Online service to translate C declarations into English and vice versa. Public domain.
cinclude2dot - Graphs include dependencies in a project using Graphviz. GPL-1.0-or-later or GPL-2.0-or-later or GPL-3.0-or-later
ClangCheck - Static analysis tool, designed to work with Clang. NCSA
conan.io - Something of a package manager for C. MIT.
Cppcheck - Static analysis tool. Despite the name, works well with C. GPL-3.0-or-later
Glade - RAD tool to enable quick development of GTK+ GUIs. GPL-2.0-only
GMSL - GNU Make Standard Library; a collection of additional functionality for GNU Make. BSD-3-Clause
GNU Global - Source code tagging tool. GPL-3.0-only
GPP - General-purpose preprocessor. More versatile than the C preprocessor, but more flexible than m4. LGPL-3.0-or-later
Highlight - Converts source code to formatted text with nice highlighting. GPL-3.0-only
include-what-you-use - Helps find unecessary inclusions and make suggestions for fixing them. Based on LLVM/Clang (and only works with it). NCSA
incbin - Include binary files in your C/C++ applications with ease Unlicense
indent - Formats C source code automatically to make it easier to read. Also converts from one style of source to another. GPL-3.0-or-later
SMACK - Modular software verification toolchain and a self-contained software verifier. Currently only works with programs compiled using Clang. MIT
unifdef - Removes #ifdef and #if directives with their delimited text without touching any other part of the file. BSD-3-Clause or BSD-2-Clause

Utilities

A 'catch-all' category for anything that doesn't fit well anywhere else.

ApeTagLibs - Library for working with APEv2 tags. MIT
argparse - Command-line argument parsing library, inspired by Python's argparse module. MIT
attr - Commands for manipulating filesystem extended attributes. GPL-2.0-or-later
bfd - Library for manipulating binary object files. Part of GNU binutils. GPL-3.0-or-later
Caffeine - Library for building daemons and services for Linux and FreeBSD systems. LGPL-2.1-or-later
CException - Implementation of exceptions. MIT
CommonMark - Implementation of the CommonMark spec.
cosmopolitan - fast portable static native textmode containers (build C programs for Linux\Mac\Windows in one go) Variety of licenses, all open source.
cpu_features - Get CPU features at runtime. Apache-2.0.
CRIU - Checkpoint/Restore In Userspace; a software tool (with a C API) for 'freezing' a running application to disk, then restoring it. GPL-2.0-only or LGPL-2.1-only
D-Bus - Simple way for applications to talk to one another. AFL-2.1 or GPL-2.0-or-later
Discount - Simple implementation of a Markdown parser. BSD-3-Clause
dlx - Implementation of Knuth's Algorithm X, with example solvers. GPL-3.0-or-later
docopt.c - Implementation of a command-line option parser. MIT
dyncall - Another foreign function interface library. MIT
GNU FreeIPMI - In-band and out-of-band IPMI implementation. GPL-3.0-only
GNU gperf - Perfect hash function generator, given a list of strings. Outputs C code. GPL-3.0-or-later
GNU Libffcall - Collection of libraries for building foreign function interfaces. GPL-3.0-or-later
Hoedown - Fully standards-compliant, extension-supporting, UTF-8 aware, fast Markdown parser. MIT
Kitsune - Efficient, general-purpose framework for dynamic software updating. LGPL-3.0-or-later
libCello - Library introducing higher-level programming to C. BSD-3-Clause
libcmark - Library for parsing the CommonMark dialect of Markdown. BSD-2-Clause
libcoap - Implementation of the Constrained Application Protocol. GPL-2.0-or-later or BSD-2-Clause
libcox - Library which permits cross-platform system calls and standard utilities across different operating systems. BSD-2-Clause
libffi - Portable foreign-function interface library. MIT
libgeohash - Pure C implementation of the Geohash algorithm. BSD-3-Clause
libgit2 - Portable implementation of the Git core methods, provided as a re-entrant linkable library. Custom license.
libgss - Generic Security Service. GPL-3.0-or-later
libimobiledevice - Cross-platform protocol library to communicate with iThings. LGPL-2.1-or-later
libnfc - Platform-independent Near-Field Communication library. LGPL-3.0-only
libpostal - Library for parsing and normalization of street addresses around the world. Powered by statistical NLP and open geo data. MIT
libtrading - Implementation of network protocols for communicating with exchanges, dark pools and other trading venues. Supports FIX, FIX/FAST and many proprietary protocols. BSD-2-Clause
libusb - Provides generic access to USB devices. LGPL-2.1-or-later
libuv - Cross-platform asynchronous I/O. MIT
libvldmail - Your friendly email validation library. No external dependencies (not even regexps). WTFPL
linenoise - Small, self-contained alternative to readline and libedit. BSD-2-Clause
libXDGdirs - An implementation of XDG Base Directory Specification MIT
MegaMimes - Library for getting the MIME types of a file. MIT
ncurses - Coloured terminal UI library. MIT
netbsd-curses - Simplified and small version of ncurses, with the same interface. BSD-3-Clause
nope.c - Ultra-light software platform for scalable server-side and networking applications (think node.js for C programmers). GPL-2.0-only
obj.h - A single-header supports OOP in pure C. MIT
parg - A single-file reimplementation of getopt with better defaults. CC0-1.0
pbc - Protocol buffers library. MIT
progressbar - Easy-to-use library for displaying text progress bars. BSD-3-Clause
rabbitmq-c - Client library for RabbitMQ. MIT
Ragel - DSL for state machines that compiles to C. GPL-2.0-only
rmw - safe-remove utility for the command line that can purge items from your waste directories after x number of days. GPL-3.0-or-later
Rogueutil - Cross-platform library for creating text-based user interfaces (TUI) Apache-2.0
sort - Collection of sorting routines, which type-specialize at compile-time with a user-defined type. MIT
termbox - Library for writing text-based interfaces. MIT
tinyexpr - Tiny recursive-descent parser, compiler and evaluation engine for simple mathematical expressions. BSD-3-Clause
tm - ⏱ Timer and Timeline Utils for C. MIT
Tulip Indicators - Library of functions for technical analysis of financial data. LGPL-3.0-or-later
whereami - One-file library for locating the current executable on the file system. WTFPL
XLSX I/O - Cross-platform library for reading and writing .xlsx files. MIT
xlsx_drone - Fast Microsoft Excel's *.xlsx reader. MIT
zlog - Reliable, pure C logging library. LGPL-2.1-only
zproto - Protocol framework for ZeroMQ. MIT
Metalang99 - Full-blown preprocessor metaprogramming. MIT
Datatype99 - Algebraic data types for C99. MIT
EasyLogger - An ultra-lightweight, high-performance C/C++ log library. MIT

Web Frameworks

Comprehensive and integrated solutions for building the next brilliant web application in C.

Concord - A Discord API wrapper library written in C. MIT
facil.io - Mini-framework for web applications. Includes a fast HTTP and Websocket server, and also supports custom protocols. MIT
kcgi - CGI and FastCGI library for C ISC.
KLone - Fully featured, multi-platform, web application development framework, targeted especially at embedded systems and appliances. BSD-3-Clause
Kore - Easy-to-use web application framework for writing scalable web APIs in C. ISC

Windows Environments

Technologies designed to bring Windows into the 21st century with respect to support for C.

Cygwin - Designed to emulate a POSIX-compatible environment extensively under Windows. Various licenses, all open source.
MinGW-w64 - Minimalist environment for C development on Windows with 64 bit support. Various licenses, all open source.
MSYS2 - Minimal SYStem 2; aims to provide support for a POSIX environment on Windows, with a package manager based on Arch Linux's pacman. Packages have individual licenses, otherwise, as MinGW and Cygwin.