Next.js 15 App Router Mastery

Next.js 15 introduces revolutionary changes to the App Router, making full-stack development more intuitive and powerful than ever.

Server Actions

Server Actions allow you to run server-side code directly from your components:

'use server'
export async function createPost(formData: FormData) {
  const title = formData.get('title')
  const content = formData.get('content')
  // Server-side logic
  await db.posts.create({
    data: { title, content }
  })
  revalidatePath('/posts')
}

Parallel Routes

Load multiple pages simultaneously with parallel routes:

// app/layout.tsx

export default function Layout({
  children,
  modal
}: {
  children: React.ReactNode
  modal: React.ReactNode
}) {
  return (
    <>
      {children}
      {modal}
    
  )
}

Intercepting Routes

Create modal experiences that intercept route navigation:

// app/posts/[id]/page.tsx (modal)

export default function PostModal({ params }: { params: { id: string } }) {
  // Modal implementation
}

Performance Improvements

Migration from Pages Router

npx @next/codemod app-router-migration

Advanced Patterns

Loading States

export default function Loading() {

  return 
Loading...

}

Error Boundaries

export default function Error({

  error,
  reset,
}: {
  error: Error & { digest?: string }
  reset: () => void
}) {
  return (
    

      
Something went wrong!

       reset()}>Try again
    

  )
}

Best Practices

1. Use Server Components by default

2. Keep client components minimal

3. Leverage Server Actions for data mutations

4. Implement proper loading and error states

5. Use parallel routes for complex layouts

Conclusion

Next.js 15's App Router represents the future of React development, providing developers with powerful tools to build better applications faster.