Next.js App Router Patterns
Comprehensive patterns for Next.js 14+ App Router architecture, Server Components, and modern full-stack React development.
When to Use This Skill
- Building new Next.js applications with App Router
- Migrating from Pages Router to App Router
- Implementing Server Components and streaming
- Setting up parallel and intercepting routes
- Optimizing data fetching and caching
- Building full-stack features with Server Actions
Core Concepts
1. Rendering Modes
| Mode | Where | When to Use |
|---|---|---|
| Server Components | Server only | Data fetching, heavy computation, secrets |
| Client Components | Browser | Interactivity, hooks, browser APIs |
| Static | Build time | Content that rarely changes |
| Dynamic | Request time | Personalized or real-time data |
| Streaming | Progressive | Large pages, slow data sources |
2. File Conventions
app/
├── layout.tsx # Shared UI wrapper
├── page.tsx # Route UI
├── loading.tsx # Loading UI (Suspense)
├── error.tsx # Error boundary
├── not-found.tsx # 404 UI
├── route.ts # API endpoint
├── template.tsx # Re-mounted layout
├── default.tsx # Parallel route fallback
└── opengraph-image.tsx # OG image generation
Quick Start
// app/layout.tsx
import { Inter } from 'next/font/google'
import { Providers } from './providers'
const inter = Inter({ subsets: ['latin'] })
export const metadata = {
title: { default: 'My App', template: '%s | My App' },
description: 'Built with Next.js App Router',
}
export default function RootLayout({
children,
}: {
children: React.ReactNode
}) {
return (
<html lang="en" suppressHydrationWarning>
<body className={inter.className}>
<Providers>{children}</Providers>
</body>
</html>
)
}
// app/page.tsx - Server Component by default
async function getProducts() {
const res = await fetch('https://api.example.com/products', {
next: { revalidate: 3600 }, // ISR: revalidate every hour
})
return res.json()
}
export default async function HomePage() {
const products = await getProducts()
return (
<main>
<h1>Products</h1>
<ProductGrid products={products} />
</main>
)
}
Detailed patterns and worked examples
Detailed pattern documentation lives in references/details.md. Read that file when the navigation tier above is insufficient.
Best Practices
Do's
- Start with Server Components - Add 'use client' only when needed
- Colocate data fetching - Fetch data where it's used
- Use Suspense boundaries - Enable streaming for slow data
- Leverage parallel routes - Independent loading states
- Use Server Actions - For mutations with progressive enhancement
Don'ts
- Don't pass serializable data - Server → Client boundary limitations
- Don't use hooks in Server Components - No useState, useEffect
- Don't fetch in Client Components - Use Server Components or React Query
- Don't over-nest layouts - Each layout adds to the component tree
- Don't ignore loading states - Always provide loading.tsx or Suspense