Next.js 14 to Next.js 15 Complete Migration Guide

⚡ Automated 1-Line Codemod

npx @next/codemod@latest next-async-request-api .

🚨 Breaking Changes List

• Page and layout props `params` and `searchParams` are now Promises and must be awaited.
• `cookies()` and `headers()` from `next/headers` return Promises and must be awaited.
• `fetch` requests in Server Components are no longer cached by default (`cache: 'no-store'` is default).
• Turbopack is now the default dev server (`next dev --turbo`).

🔧 Verified Migration Diff

// Next.js 14 -> 15 Route Parameters Migration
- export default function Page({ params }: { params: { id: string } }) {
-   const { id } = params;
-   return <div>ID: {id}</div>;
- }
+ export default async function Page({ params }: { params: Promise<{ id: string }> }) {
+   const { id } = await params;
+   return <div>ID: {id}</div>;
+ }