Doxygen vs Natural Docs

Doxygen is a free documentation generator that turns source-code comments into reference material, parsing items such as classes, functions and variables. It supports C/C++, Lex, Java, Python, VHDL, PHP IDL, C#, Fortran, Objective-C 2.0 and some D sources. Output can be generated as HTML, PDF through LaTeX, Word through RTF or structured XML for external tools. Graphviz’s dot tool can add include-dependency, collaboration, call, directory-structure and class-hierarchy diagrams. Doxywizard provides a graphical interface for editing settings and running the generator on Windows, Linux and macOS; Doxygen also works on many Unix flavors. It supports HTML Help, docsets, Qt-Help and Eclipse Help, with more than 100 configurable options. The tool runs without registration and does not collect personal or usage data. It is self-hosted and licensed under the GNU General Public License, without express or implied warranty. Help is listed through Stack Overflow and the doxygen users mailing list; commercial feature and bug-fix support has limited capacity.

Natural Docs is a command-line documentation generator that scans source-code comments and text files to create HTML documentation, including API references. Its syntax is designed to read like ordinary English in both source code and generated pages. The project says it comes configured for 25 programming languages and can be extended; for certain languages, it can also read Javadoc and Microsoft XML comments without rewrites. Generated pages have three panels, dynamic navigation, search and summaries that appear when readers hover over links. They can be opened from a local hard drive without installed software, and styled with custom CSS and images. Natural Docs runs on Linux, macOS and Windows. It is free and open source under AGPL version 3. The license requires source availability for modified distributions, projects incorporating its source, and services incorporating its functionality; merely documenting a project does not place that project under AGPL. Help is available through a Reddit forum, email and GitHub issues, with commercial support contracts available to businesses.