Server components are no longer opt-in
Next.js 16 makes React Server Components the default for all new projects. Every component is a server component unless you explicitly add 'use client'.
This is a big shift. It means less JavaScript shipped to the browser by default, faster initial page loads, and a simpler mental model once you get used to it.
What changed
The App Router is now the only supported router — Pages Router is officially deprecated. Turbopack is the default bundler. And the new next/cache API makes data fetching and revalidation much cleaner.