# The Complete Guide to Next.js App Router Next.js 14 introduced the stable App Router, a paradigm shift in how we build React applications. Let's explore everything you need to know. ## Understanding the App Router The App Router uses React Server Components by default, offering: - **Better performance** through server-side rendering - **Smaller bundle sizes** by keeping code on the server - **Improved SEO** with pre-rendered content ## File-Based Routing The App Router uses a folder-based routing system: ``` app/ ├── page.tsx # / ├── about/ │ └── page.tsx # /about ├── blog/ │ ├── page.tsx # /blog │ └── [slug]/ │ └── page.tsx # /blog/:slug ``` ## Layouts and Templates ### Root Layout Every app needs a root layout: ```tsx export default function RootLayout({ children, }: { children: React.ReactNode; }) { return ( {children} ); } ``` ### Nested Layouts Create layouts at any level to share UI across routes: ```tsx // app/blog/layout.tsx export default function BlogLayout({ children, }: { children: React.ReactNode; }) { return (

{children}

); } ``` ## Loading UI Add loading.tsx files for automatic loading states: ```tsx // app/blog/loading.tsx export default function Loading() { return ; } ``` ## Error Handling Handle errors gracefully with error.tsx: ```tsx 'use client'; export default function Error({ error, reset, }: { error: Error; reset: () => void; }) { return (

Something went wrong!

); } ``` ## Conclusion The App Router represents the future of Next.js development. Embrace server components, leverage the new conventions, and build faster, more scalable applications.

React

Building Scalable React Applications in 2024

The Complete Guide to Next.js App Router