React Component Architecture - RSC

Core Principle: RSC as Default

All components in Next.js App Router are Server Components by default.

Server Components

• Async functions
• Can fetch data directly
• Cannot use state or effects
• Cannot use event handlers
• Cannot use browser APIs
• Run only on server

// Server Component (no 'use client')
export default async function PostPage({ params }) {
  const post = await fetchPost(params.id);