Asciidoctor

A high-speed Ruby-based text processor that converts AsciiDoc content into professional HTML5, PDF, and EPUB3 formats.

Asciidoctor serves as the definitive implementation of the AsciiDoc markup language (originally created by Stuart Rackham). Lead developer Dan Allen maintains this Ruby-based engine to deliver speeds up to 40x faster than the legacy Python toolchain. It integrates natively with build tools like Gradle, Maven, and Ant while powering documentation for major platforms (GitHub and GitLab). Users generate professional output (HTML5, PDF, and man pages) from plain-text files using a modular extension API and a comprehensive CSS-based styling system.

https://asciidoctor.org