# 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.