Next.js 16: what changed and how to prepare your project

Next.js 16 shipped on October 21, 2025, and over the following year the branch received four minor releases — from 16.1 in December 2025 to 16.4 in October 2026. We use Next.js 16 for Webstar Host and the R&B Team website, so here is what actually changed in day-to-day work.

The essentials of Next.js 16

• Turbopack is the default bundler for both development and production builds. Webpack is still available via the --webpack flag if your project depends on specific plugins.
• proxy.ts replaces middleware.ts. The new file runs on Node.js. The old middleware.ts is still supported for Edge cases but is deprecated.
• Cache Components and the "use cache" directive. The new caching model is enabled with cacheComponents: true and replaces experimental PPR. You mark explicitly what gets cached instead of wondering why a page suddenly became static.
• New cache APIs: updateTag() and refresh() in Server Actions, and revalidateTag() now requires a second argument — the cache profile.
• React 19.2: View Transitions, useEffectEvent and the <Activity/> component.
• React Compiler support — enabled with reactCompiler: true, off by default.

What was removed

• AMP support.
• The next lint command — linting is now configured directly with ESLint or Biome.
• Synchronous access to params, cookies() and headers(): only with await now.

Minimum requirements: Node.js 20.9+ and TypeScript 5.1+.

16.x minor releases

• 16.1 (December 2025): on-disk Turbopack caching in development, a bundle analyzer, easier Node.js debugging.
• 16.2 (March 2026): a stable Adapter API, AGENTS.md in the create-next-app template, Server Fast Refresh.
• 16.3 (August 2026): Instant Navigations and tooling for AI agents.
• 16.4 (October 2026): lazy route compilation in development.

Why upgrades are a security matter

In December 2025 a critical vulnerability was found in React Server Components (CVE-2025-66478), and several more Next.js security releases followed during 2026. A project that "works, so nobody touches it" on an old version gradually becomes a risk. Small regular upgrades cost far less than one big migration two years later.

Migration checklist from Next.js 15

1. Upgrade Node.js to 20.9+ everywhere: locally, in CI and on the server.
2. Rename middleware.ts to proxy.ts and check redirect and localisation logic.
3. Replace synchronous access to params, cookies() and headers() with async calls.
4. Build with Turbopack; if something fails, use --webpack temporarily and plan a fix.
5. Update revalidateTag() calls and review your caching strategy.
6. Set up linting without next lint.
7. Run e2e tests for key flows: sign-in, forms, payments.

If your project runs on Next.js 13–15 and you're not sure where to start, we'll audit it and propose a step-by-step upgrade plan with no downtime.