You may have spotted that MDN has a new frontend. There's plenty happening under the surface, so let's unpack the technologies we chose, the architectural decisions we made, and why we did a rebuild at all.

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MDN rebuilt its frontend from a React SPA (called 'yari') to a web components-based architecture using Lit, eliminating technical debt accumulated from ejected Create React App configs, entangled CSS, and the fundamental mismatch between a React wrapper and static documentation content. The new stack uses Lit web components for islands of interactivity, custom server components for static HTML templating, and Rspack (a Rust-based Webpack-compatible bundler) for builds. Key architectural wins include lazy-loading web components by name convention, shipping only the CSS needed per page, progressive enhancement via Declarative Shadow DOM, and a development environment that starts in 2 seconds instead of 2 minutes. The Baseline project guided browser compatibility decisions throughout.

Under the hood of MDN's new frontend

Server components and web components (on the server)