React 19 Server Components Patterns

React Server Components change the fundamental mental model of React development. Instead of shipping a JavaScript bundle that fetches data on the client, Server Components run on the server, fetch data directly, and send rendered HTML to the browser. The result: faster initial page loads, smaller JavaScript bundles, and direct access to databases, file systems, and internal APIs without building an API layer. But the transition from client-first React to server-first React requires new patterns. This guide covers the practical patterns you need to build production applications with React 19 Server Components. The first principle: components are server components by default. You do not need to add any directive.