nextjs 15

@next/codemod CLI: Upgrade seamlessly to the latest versions of Next.js and React with this command-line tool.

Async Request APIs (Breaking): Request-specific APIs are now asynchronous, paving the way for future optimizations. A codemod is provided to help with migration.

Caching Semantics (Breaking): By default, fetch requests, GET Route Handlers, and client-side navigations are no longer cached. However, caching can be manually enabled.

React 19 Support: Next.js 15 includes support for React 19, with experimental features like the React Compiler and improved error handling during hydration.

Turbopack Dev (Stable): Turbocharged development performance with faster startup times and more responsive code updates, thanks to Turbopack.

Static Indicator: A new visual indicator in development mode to highlight static routes, making optimization easier.

unstable_after API (Experimental): A new API that lets you run code after streaming a response, ideal for tasks like logging and analytics.

instrumentation.js API (Stable): This new server lifecycle API improves observability, offering integrations with tools like OpenTelemetry.

Enhanced Forms (next/form): The

component enhances regular HTML forms by adding client-side navigation and prefetching capabilities.

TypeScript Support for next.config.ts: Improved TypeScript integration for next.config.ts, offering type safety, autocompletion, and better developer experience.

Self-hosting Improvements: New features for self-hosting, including more control over Cache-Control headers, optimized image handling, and automatic use of sharp for image processing.

Server Actions Security: Server actions are now more secure with unique action IDs and automatic cleanup of unused actions.

Bundling External Packages (Stable): Automatic bundling for external packages is now supported for both the App and Pages Routers, with new configuration options.

ESLint 9 Support: Full compatibility with ESLint 9, ensuring smooth transitions while maintaining backward compatibility.

Performance Improvements: Build times and Fast Refresh speeds have been significantly optimized, making the development process even faster and smoother.