BookStack is a free and open source knowledge management platform built on PHP. The system has been built around simplicity to ensure that adding information to it is not a chore. The content structure is built on the metaphors of Books, Chapters & Pages.

GitBook is a tool for building beautiful books using Git and Markdown. It can generate your book into multiple formats:

MkDocs is static site generator that's geared towards building project documentation. Documentation source files are written in Markdown, and configured with a single YAML configuration file.

Docsie is a collaboration software for software docs, intranets and knowledge management. Easily create your software documentation in Docsie and embed it into your site or internal portal with a string of JavaScript.

Vrite is an open-source headless CMS intended for technical content like programming blogs or documentation. It aims to provide the best user and developer experience for creating, managing and delivering technical content, with features like:

Read the Docs hosts documentation for the open source community. It supports Sphinx docs written with reStructuredText, and can pull from your Subversion, Bazaar, Git, and Mercurial repositories. The code is open source, and available on github.

ReadMe is a completely customizable and collaborative place for dynamic API and/or product documentation. Users can play around with the API right in the docs, automatically generated from a Swagger / OAS file. It also works as a knowledge base platform.