lowdown is a Markdown translator producing HTML5 and roff documents in
the ms and man formats. It's just clean, secure, open source C code with
no dependencies. Its canonical documentation is lowdown(1) for the
formatter, lowdown(5) for the syntax, and the library interface at
lowdown(3).

lowdown started as a fork of hoedown to add sandboxing (pledge(2),
capsicum(4), or sandbox_init(3)) and roff output to securely generate
PDFs on OpenBSD with just mandoc(1).

It has grown to admit many more extensions and outputs, and can even be
used to show the difference between two Markdown documents with
lowdown-diff, documented as the lowdown diffing engine. This uses a
tree-based difference algorithm to show semantically-valid Markdown
differences.