app-router

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This skill should be used when the user asks to "create a Next.js route", "add a page", "set up layouts", "implement loading states", "add error boundaries", "organize routes", "create dynamic routes", or needs guidance on Next.js App Router file conventions and routing patterns.

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Sourcedavepoon/buildwithclaude

Added on2026-02-23

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npx skill4agent add davepoon/buildwithclaude app-router

SKILL.md Content

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Next.js App Router Patterns

Overview

The App Router is Next.js's file-system based router built on React Server Components. It uses a

app/

directory structure where folders define routes and special files control UI behavior.

Core File Conventions

Route Files

Each route segment is defined by a folder. Special files within folders control behavior:

File	Purpose
`page.tsx`	Unique UI for a route, makes route publicly accessible
`layout.tsx`	Shared UI wrapper, preserves state across navigations
`loading.tsx`	Loading UI using React Suspense
`error.tsx`	Error boundary for route segment
`not-found.tsx`	UI for 404 responses
`template.tsx`	Like layout but re-renders on navigation
`default.tsx`	Fallback for parallel routes

Folder Conventions

Pattern	Purpose	Example
`folder/`	Route segment	`app/blog/` → `/blog`
`[folder]/`	Dynamic segment	`app/blog/[slug]/` → `/blog/:slug`
`[...folder]/`	Catch-all segment	`app/docs/[...slug]/` → `/docs/*`
`[[...folder]]/`	Optional catch-all	`app/shop/[[...slug]]/` → `/shop` or `/shop/*`
`(folder)/`	Route group (no URL)	`app/(marketing)/about/` → `/about`
`@folder/`	Named slot (parallel routes)	`app/@modal/login/`
`_folder/`	Private folder (excluded)	`app/_components/`

Creating Routes

Basic Route Structure

To create a new route, add a folder with

page.tsx

:

app/
├── page.tsx              # / (home)
├── about/
│   └── page.tsx          # /about
└── blog/
    ├── page.tsx          # /blog
    └── [slug]/
        └── page.tsx      # /blog/:slug

Page Component

A page is a Server Component by default:

tsx

// app/about/page.tsx
export default function AboutPage() {
  return (
    <main>
      <h1>About Us</h1>
      <p>Welcome to our company.</p>
    </main>
  )
}

Dynamic Routes

Access route parameters via the

params

prop:

tsx

// app/blog/[slug]/page.tsx
interface PageProps {
  params: Promise<{ slug: string }>
}

export default async function BlogPost({ params }: PageProps) {
  const { slug } = await params
  const post = await getPost(slug)

  return <article>{post.content}</article>
}

Layouts

Root Layout (Required)

Every app needs a root layout with

<html>

and

<body>

:

tsx

// app/layout.tsx
export default function RootLayout({
  children,
}: {
  children: React.ReactNode
}) {
  return (
    <html lang="en">
      <body>{children}</body>
    </html>
  )
}

Nested Layouts

Layouts wrap their children and preserve state:

tsx

// app/dashboard/layout.tsx
export default function DashboardLayout({
  children,
}: {
  children: React.ReactNode
}) {
  return (
    <div className="flex">
      <Sidebar />
      <main className="flex-1">{children}</main>
    </div>
  )
}

Loading and Error States

Loading UI

Create instant loading states with Suspense:

tsx

// app/dashboard/loading.tsx
export default function Loading() {
  return <div className="animate-pulse">Loading...</div>
}

Error Boundaries

Handle errors gracefully:

tsx

// app/dashboard/error.tsx
'use client'

export default function Error({
  error,
  reset,
}: {
  error: Error
  reset: () => void
}) {
  return (
    <div>
      <h2>Something went wrong!</h2>
      <button onClick={reset}>Try again</button>
    </div>
  )
}

Route Groups

Organize routes without affecting URL structure:

app/
├── (marketing)/
│   ├── layout.tsx        # Marketing layout
│   ├── about/page.tsx    # /about
│   └── contact/page.tsx  # /contact
└── (shop)/
    ├── layout.tsx        # Shop layout
    └── products/page.tsx # /products

Metadata

Static Metadata

tsx

// app/about/page.tsx
import { Metadata } from 'next'

export const metadata: Metadata = {
  title: 'About Us',
  description: 'Learn more about our company',
}

Dynamic Metadata

tsx

// app/blog/[slug]/page.tsx
export async function generateMetadata({ params }: PageProps): Promise<Metadata> {
  const { slug } = await params
  const post = await getPost(slug)
  return { title: post.title }
}

Key Patterns

Colocation: Keep components, tests, and styles near routes
Private folders: Use
```
_folder
```
for non-route files
Route groups: Use
```
(folder)
```
to organize without URL impact
Parallel routes: Use
```
@slot
```
for complex layouts
Intercepting routes: Use
```
(.)
```
patterns for modals

Resources

For detailed patterns, see:

```
references/routing-conventions.md
```
- Complete file conventions
```
references/layouts-templates.md
```
- Layout composition patterns
```
references/loading-error-states.md
```
- Suspense and error handling
```
examples/dynamic-routes.md
```
- Dynamic routing examples
```
examples/parallel-routes.md
```
- Parallel and intercepting routes