MkDocs is a static site generator built specifically for project documentation. Its own site describes it as “a fast, simple and downright gorgeous static site generator that’s geared towards building project documentation.” First released in 2014, it took a deliberately narrow focus compared with general-purpose site generators: it exists to turn a folder of documentation into a clean, navigable documentation website.
Authors write content in Markdown, the lightweight markup that most developers already know, and configure the site through a single YAML file. That configuration defines the navigation structure, theme, and options, while the Markdown files supply the content. Markdown extensions can be enabled to add capabilities beyond the base syntax, such as admonitions, footnotes, and richer code handling, without abandoning the simplicity of plain-text authoring.
The output is a completely static HTML site with no server-side processing required. As the documentation notes, the generated site can be hosted “on GitHub Pages, Amazon S3, or anywhere else you choose.” This makes MkDocs sites cheap to host, fast to serve, and easy to deploy through ordinary continuous integration, since a build step produces a tree of files that any static host or content delivery network can serve.
MkDocs owes much of its popularity to its theme ecosystem, and in particular to Material for MkDocs, a polished and heavily featured theme that became one of the most recognizable looks in open-source documentation. The combination of Markdown authoring, simple YAML configuration, and the Material theme made MkDocs a default choice for many projects that wanted attractive documentation without the heavier reStructuredText workflow of Sphinx. The source is maintained openly on GitHub under the mkdocs organization.
Where Sphinx anchors the reStructuredText side of the documentation world, MkDocs anchors the Markdown side, and both sit firmly within the docs-as-code tradition. Documentation lives as version-controlled plain text, a generator turns it into a static site, and the build runs as part of the same pipeline that ships the software it describes.