Docusaurus

Docusaurus builds documentation websites from Markdown files with versioning, search, i18n, and a plugin system, all using React under the hood. It's what Meta uses for React docs, and hundreds of major open source projects use it too.

MIT license, TypeScript. The feature list is deep: versioned docs (keep v1 docs live while writing v2), i18n (built-in multi-language support), search (Algolia DocSearch integration), MDX support (React components inside Markdown), blog section, dark mode, and a plugin system. The sidebar is auto-generated from your file structure or manually configured.

Fully free. No paid tier, no premium features. The entire platform including all plugins is open source. Deployment is free on Vercel, Netlify, GitHub Pages, or any static host. Solo to large teams: free. Docusaurus scales from a personal project wiki to massive multi-version documentation sites. The ops burden is essentially zero; it generates static HTML.

The catch: it's React. Your docs site is a React app, which means slower builds than Hugo and a heavier node_modules than you'd expect for a static site. Customization beyond themes requires React knowledge. And if you don't need versioning, search, or i18n, simpler tools like VitePress or MkDocs get you there with less overhead.