Complete Guide to Next.js App Router

Next.js App Router represents a paradigm shift in how we build React applications. This guide will help you understand the key concepts and best practices.

What is App Router?

The App Router is Next.js's new routing system built on React Server Components. It provides:

First-class support for React Server Components
Built-in data fetching
Nested layouts and routes
Improved performance through streaming

Key Features

1. Server Components

// app/page.tsx
export default async function Home() {
  const data = await getData(); // This runs on the server!
  return <h1>{data.title}</h1>;
}

2. Nested Layouts

// app/layout.tsx
export default function RootLayout({ children }) {
  return (
    <html>
      <body>{children}</body>
    </html>
  );
}

3. Data Fetching

Next.js 13+ simplifies data fetching with built-in functions:

async function getData() {
  const res = await fetch("https://api.example.com/data");
  return res.json();
}

Best Practices

Use Server Components by default
Client Components when needed (interactivity)
Colocate data fetching with components
Leverage streaming for improved UX

Conclusion

The App Router is a powerful tool that helps build better React applications. Understanding these concepts will help you make the most of Next.js's capabilities.