Getting Started with Next.js App Router
File-Based Routing
The App Router uses a file-system based routing where folders define routes. Each folder represents a route segment, and special files like page.tsx, layout.tsx, and loading.tsx have specific purposes. To create a route, simply create a folder in the app directory and add a page.tsx file. Nested folders create nested routes. This intuitive structure makes it easy to understand your application's routing at a glance.
Layouts and Templates
Layouts are UI that's shared between routes. They don't re-render on navigation, making them perfect for navigation bars, sidebars, and other persistent UI. Create a layout.tsx file in any folder to wrap all child routes. Layouts can be nested, allowing you to compose complex page structures. Templates are similar but re-render on navigation, useful for animations or when you need fresh state on each navigation.
Server and Client Components
By default, all components in the App Router are Server Components. They render on the server, reducing client-side JavaScript. Use the 'use client' directive at the top of a file to create a Client Component when you need interactivity, browser APIs, or React hooks like useState. The key is to use Server Components by default and Client Components only when necessary. This maximizes performance while maintaining full React functionality.
Data Fetching Patterns
Data fetching in the App Router is straightforward. Server Components can be async and fetch data directly using fetch or database queries. Next.js automatically deduplicates requests, caches responses, and provides revalidation strategies. Use loading.tsx for loading states and error.tsx for error boundaries. For dynamic data, use revalidation strategies or opt out of caching. The result is a simple, powerful data fetching model that works seamlessly with React Suspense.
The Next.js App Router is a powerful foundation for modern web applications. By understanding its core concepts—file-based routing, layouts, Server Components, and data fetching—you can build fast, scalable applications with excellent developer experience. Start with Server Components by default, add Client Components when needed, and leverage the built-in optimizations.
James Kim
Software developer and writer sharing insights on modern web development.