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 documents. 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.