ReadTheDocs - Spend your time on writing high quality documentation, not on the tools to make your documentation work.
code_doc - Hosted documentation and artifacts server
GitBook - Modern Publishing, Simply taking your books from ideas to finished, polished books.
Vrite - Open-source, headless CMS for technical content.
Natural Docs - Natural Docs is an open-source documentation generator for multiple programming languages.
Ahrefs - Ahrefs is a toolset for SEO and marketing. We have tools for backlink research, organic traffic research, keyword research, content marketing & more. Give Ahrefs a try!