Latest 0.24.1
License BSD2
Platforms ios 5.0, osx 10.7, tvos 9.0

Build Status
Windows Build Status

cmark is the C reference implementation of CommonMark, a
rationalized version of Markdown syntax with a spec.
(For the JavaScript reference implementation, see

It provides a shared library (libcmark) with functions for parsing
CommonMark documents to an abstract syntax tree (AST), manipulating
the AST, and rendering the document to HTML, groff man, LaTeX,
CommonMark, or an XML representation of the AST. It also provides a
command-line program (cmark) for parsing and rendering CommonMark

Advantages of this library:

  • Portable. The library and program are written in standard
    C99 and have no external dependencies. They have been tested with
    MSVC, gcc, tcc, and clang.

  • Fast. cmark can render a Markdown version of War and Peace in
    the blink of an eye (127 milliseconds on a ten year old laptop,
    vs. 100-400 milliseconds for an eye blink). In our benchmarks,
    cmark is 10,000 times faster than the original, and
    on par with the very fastest available Markdown processors.

  • Accurate. The library passes all CommonMark conformance tests.

  • Standardized. The library can be expected to parse CommonMark
    the same way as any other conforming parser. So, for example,
    you can use commonmark.js on the client to preview content that
    will be rendered on the server using cmark.

  • Robust. The library has been extensively fuzz-tested using
    american fuzzy lop. The test suite includes pathological cases
    that bring many other Markdown parsers to a crawl (for example,
    thousands-deep nested bracketed text or block quotes).

  • Flexible. CommonMark input is parsed to an AST which can be
    manipulated programatically prior to rendering.

  • Multiple renderers. Output in HTML, groff man, LaTeX, CommonMark,
    and a custom XML format is supported. And it is easy to write new
    renderers to support other formats.

  • Free. BSD2-licensed.

It is easy to use libcmark in python, lua, ruby, and other dynamic
languages: see the wrappers/ subdirectory for some simple examples.

There are also libraries that wrap libcmark for
Perl, and


Building the C program (cmark) and shared library (libcmark)
requires cmake. If you modify, then you will also
need re2c (>= 0.14.2), which is used to generate scanners.c from We have included a pre-generated scanners.c in
the repository to reduce build dependencies.

If you have GNU make, you can simply make, make test, and make install. This calls cmake to create a Makefile in the build
directory, then uses that Makefile to create the executable and
library. The binaries can be found in build/src. The default
installation prefix is /usr/local. To change the installation
prefix, pass the INSTALL_PREFIX variable if you run make for the
first time: make INSTALL_PREFIX=path.

For a more portable method, you can use cmake manually. cmake knows
how to create build environments for many build systems. For example,
on FreeBSD:

mkdir build
cd build
cmake ..  # optionally: -DCMAKE_INSTALL_PREFIX=path
make      # executable will be created as build/src/cmark
make test
make install

Or, to create Xcode project files on OSX:

mkdir build
cd build
cmake -G Xcode ..
open cmark.xcodeproj

The GNU Makefile also provides a few other targets for developers.
To run a benchmark:

make bench

To run a test for memory leaks using valgrind:

make leakcheck

To reformat source code using astyle:

make astyle

To run a "fuzz test" against ten long randomly generated inputs:

make fuzztest

To do a more systematic fuzz test with american fuzzy lop:

AFL_PATH=/path/to/afl_directory make afl

To make a release tarball and zip archive:

make archive

Installing (Windows)

To compile with MSVC and NMAKE:


You can cross-compile a Windows binary and dll on linux if you have the
mingw32 compiler:

make mingw

The binaries will be in build-mingw/windows/bin.


Instructions for the use of the command line program and library can
be found in the man pages in the man subdirectory.


By default, the library will pass through raw HTML and potentially
dangerous links (javascript:, vbscript:, data:, file:).

It is recommended that users either disable this potentially unsafe
feature by using the option CMARK_OPT_SAFE (or --safe with the
command-line program), or run the output through an HTML sanitizer
to protect against
XSS attacks.


There is a forum for discussing
; you should use it instead of
github issues for questions and possibly open-ended discussions.
Use the github issue tracker
only for simple, clear, actionable issues.


John MacFarlane wrote the original library and program.
The block parsing algorithm was worked out together with David
Greenspan. Vicent Marti optimized the C implementation for
performance, increasing its speed tenfold. Kārlis Gaņģis helped
work out a better parsing algorithm for links and emphasis,
eliminating several worst-case performance issues.
Nick Wellnhofer contributed many improvements, including
most of the C library’s API and its test harness.

Latest podspec

    "name": "cmark",
    "version": "0.24.1",
    "summary": "CommonMark parsing and rendering library and program in C",
    "description": "`cmark` is the C reference implementation of [CommonMark], anrationalized version of Markdown syntax with a [spec][].n(For the JavaScript reference implementation, seen[commonmark.js].)nnIt provides a shared library (`libcmark`) with functions for parsingnCommonMark documents to an abstract syntax tree (AST), manipulatingnthe AST, and rendering the document to HTML, groff man, LaTeX,nCommonMark, or an XML representation of the AST.  It also provides ancommand-line program (`cmark`) for parsing and rendering CommonMarkndocuments.",
    "homepage": "",
    "license": "BSD2",
    "authors": {
        "John MacFarlane": "[email protected]"
    "platforms": {
        "ios": "5.0",
        "osx": "10.7",
        "tvos": "9.0"
    "source": {
        "git": "",
        "tag": "0.24.0"
    "source_files": [
    "public_header_files": [
    "prepare_command": "echo `pwd`nsed -i '' 's/include <\(cmark.*\)>/include "\1"/' src/cmark.hnmkdir -p build; cd build && cmake -G Xcode .."

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