Universal markup converter
Pandoc is a universal markup converter written in Haskell that functions both as a library and a command-line tool for converting between dozens of document formats, including Markdown, HTML, LaTeX, Word, PDF, PowerPoint, EPUB, and many others. The project uses a modular architecture composed of readers (which parse input formats into an abstract syntax tree) and writers (which convert that AST to target formats), and supports customization through Lua filters for modifying documents during conversion. John MacFarlane created and maintains the project, which also includes a Lua scripting engine for writing custom filters and readers, and a separate HTTP server library for accessing pandoc's conversion capabilities programmatically.