Next.js 15: What's New and Should You Upgrade?

What's New in Next.js 15?

Next.js 15 brings significant improvements over version 14. Here's everything you need to know.

Key Changes

1. Turbopack is Now Stable

Turbopack, the Rust-based bundler, is now production-ready:

• Up to 70% faster local development
• Significantly reduced memory usage
• Better HMR (Hot Module Replacement)

Enable it with: next dev --turbo

2. New Caching Defaults

Breaking Change: Caching behavior has changed significantly.

Next.js 14:

• fetch requests cached by default
• Route handlers cached by default

Next.js 15:

• fetch requests NOT cached by default
• Route handlers NOT cached by default
• You must explicitly opt into caching

3. Async Request APIs

Headers, cookies, and params are now async. You need to await them:

• const { id } = await params;
• const cookieStore = await cookies();
• const headersList = await headers();

4. React 19 Support

Next.js 15 supports React 19 features:

• Server Components improvements
• Better Suspense handling
• New hooks and APIs

Should You Upgrade?

Upgrade If:

• Starting a new project
• Need faster development builds
• Want explicit control over caching
• Ready to update async APIs

Wait If:

• Large codebase with many fetch calls
• Tight deadline (breaking changes need testing)
• Critical production app without test coverage

Migration Steps

1. Update dependencies
2. Run the Next.js codemod
3. Update async APIs manually
4. Review and update caching strategy
5. Test thoroughly

My Recommendation

For new projects, use Next.js 15. For existing projects, plan the migration carefully and test all caching behavior.

Need help with your Next.js project? Let's discuss.