Next.js 15 Release Notes

@next/codemod CLI: Automatic upgrade to the latest Next.js and React versions is now available.

Async APIs: headers, cookies, params, and searchParams have been changed to async. Await is required.

Fetch requests: Default caching is disabled; cache: 'force-cache' must be explicitly specified to enable caching.

GET Route Handlers: Default caching is disabled; requires setting export const dynamic = 'force-static'.

Client Router Cache: Default caching is disabled; configurable via staleTimes setting.

React 19 Support: Official support for React 19, including React Compiler (experimental) and improved hydration errors.

Turbopack Stabilization: Improved performance and stability for the development environment.

Static Route Indicator: Visual indicator for static routes has been added.

unstable_after API (Experimental): Enables running code after response streaming completes.

instrumentation.js API (Stable): API added for observing the server lifecycle.

next/form: HTML form and client-side navigation integration.

next.config.ts Support: next.config files can now be written in TypeScript.

Self-hosting Improvements: Enhanced control over Cache-Control headers.

Server Actions Security: Improved security through unpredictable endpoint generation and dead code elimination.

External Package Bundling (Stable): New configuration options for App and Pages routers.

ESLint 9 Support: Support for ESLint version 9.

Dev and Build Performance: Reduced build times and faster Fast Refresh.