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

b63

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

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

flint

Zero-config, manifest-first C/C++ build system and package manager with direct Git dependency resolution. MIT

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.

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

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

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.

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

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

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

Owi

A symbolic execution tool (paper) AGPL-3.0-or-later

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

vfs-pipe

One-header library to expose internal C variables as a virtual filesystem for live inspection and tuning. MIT

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

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

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

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.

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

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.

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

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

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

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

Languages such as C, C++, Java, and Perl, and the Android™ platform.

tinyc.game

Tiny C games you can compile and run RIGHT NOW http://tinyc.games MIT

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

8 gdb tricks you should know

10 C99 tricks

A comprehensive MPI tutorial resource

Build Your Own Text Editor

Diving into concurrency: trying out mutexes and atomics

Generic C reference counting

How to write portable C without complicating your build

Introduction to OpenMP

(video)

OpenMP tutorial

(for the OpenMP3 standard)

MPI tutorial

Scalable C - Writing Large-Scale Distributed C

Some unknown features or tricks in C language

What every C programmer should know about undefined behaviour

part 2 part 3

Advanced metaprogramming in C

A quick tutorial on implementing and debugging malloc, free, calloc, and realloc

Bit twiddling hacks

Implementing smart pointers for the C programming language

Inline functions in C

Metaprogramming custom control structures in C

Solving the temporary storage problem of C macros

Some dark corners of C

Writing efficient C and C code optimization

Compiling Algebraic Data Types in Pure C99

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.

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.

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.

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.

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.

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

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

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

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

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

pdfio

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

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

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

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]

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

CTL

C CONTAINER TEMPLATE LIBRARY (CTL) MIT

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

libzip

C library for reading, creating and modifying zip archives. 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

libcsv

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

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

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

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

Expat

Stream-oriented XML parser. MIT

libxml2

Standards-compliant, portable XML parser. MIT

xml

Simple, low-memory-use XML parser / tokenizer. MIT

libYAML

YAML 1.1 parser and emitter. MIT

SAIL

⛵ The missing small and fast image decoding library for humans (not for machines) MIT

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

Owi

A symbolic execution tool (paper) AGPL-3.0-or-later

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

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

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

ApeTagLibs

Library for working with APEv2 tags. MIT

argparse

Command-line argument parsing library, inspired by Python's argparse module. MIT

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.

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

microlog

Extensible and configurable logging library with topics for embedded and desktop MIT

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

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.