nextjs-app-router-fundamentals

Next.js App Router requires creating an app/ directory structure with layout.tsx for shared UI, page.tsx for route content, and route.ts for API handlers, replacing the previous Pages Router file conventions.

Next.js App Router handles routing and nested layouts by defining layout.tsx and page.tsx files within nested folder structures under the app/ directory, enabling hierarchical UI composition and dynamic route segments.

The best way to manage metadata and SEO in Next.js App Router is by using the built-in metadata API within layout.tsx and page.tsx files, which replaces the previous Head component and ensures compatible SEO strategies.

Yes, you can use API route handlers with Next.js App Router by creating route.ts files inside the app/ directory, which define server-side endpoints and replace the traditional pages/api/ structure.

Migrating a large Next.js codebase to App Router inherently adopts server components by default, requiring you to understand server and client component boundaries to correctly implement modern routing patterns and layouts.