Next.js 15 and the App Router: A Complete Migration Guide

Why Migrate to App Router?

Next.js 15 with the App Router represents a fundamental shift in how we build React applications, offering improved performance, simplified data fetching, and better developer experience.

Key Benefits

React Server Components: Reduce client-side JavaScript

Streaming: Progressive page rendering

Simplified Data Fetching: No more getServerSideProps

Improved Caching: Built-in request memoization

Parallel Routes: Complex layouts made simple

Migration Steps

Audit Your App: Identify pages and API routes

Set Up App Directory: Create parallel structure

Convert Layouts: Create layout.tsx files

Migrate Pages: Convert to Server Components

Update Data Fetching: Replace getServerSideProps with async components

Handle Client Interactivity: Add 'use client' where needed

Next.js 15 New Features

Turbopack for development (stable)

Partial Prerendering (experimental)

Improved TypeScript support

Enhanced security headers