Docusaurus
docusaurus.ioDocumentation
Free, open-source, and battle-tested by half of GitHub's OSS projects — the safe default for docs-as-code.
Other products from Documentation
If your product is an API, this turns your OpenAPI spec into docs devs can actually test requests against.
Point it at a GitHub repo and get a polished, AI-searchable docs site without touching a CSS file.
The default pick when you want docs that read like a real product, not a wall of Markdown.
Already on Next.js? This gets you a fast, MDX-powered docs site without adopting a second framework.