What are the key features introduced in React 19

Key Features of React 19

1. React Compiler: An experimental compiler transforms React code into optimized JavaScript, which can lead to substantial performance improvements. It manages component rendering automatically, reducing the need for manual state and UI updates, and optimizing components to minimize excessive re-rendering[1][4].

2. Server Actions: This feature streamlines data mutations and state updates, allowing client components to call asynchronous functions directly. It includes built-in error handling and provides immediate user feedback during data submissions, simplifying form handling with new props like `action` and `formAction`[2][4].

3. React Server Components (RSCs): RSCs enable server-side rendering of UI components, improving initial load times and reducing client bundle sizes. They can be executed at build time or on each request, offering flexibility in managing server and client interactions[3][4].

4. New Hooks: Several new hooks have been introduced:
- `useFormStatus()`: Helps manage form states.
- `useOptimistic()`: Facilitates optimistic UI updates.
- `useActionState()`: Streamlines state management related to actions[2][3].

5. Enhanced Error Reporting: Error handling has been improved to provide clearer messages and reduce duplication in error logs. New root options allow developers to handle caught and uncaught errors more effectively[1][2].

6. Support for Custom Elements: Full support for custom elements has been added, allowing React to treat unrecognized props as properties rather than just attributes, enhancing integration with web components[1][2].

7. Document Metadata and Asset Loading: Enhancements in managing document metadata and loading assets in the background improve both performance and user experience by optimizing resource handling[4][5].

8. Automatic Batching: React 19 introduces automatic batching, which groups multiple state updates to minimize renders and optimize performance[4][5].

9. Improved Hydration Error Reporting: The handling of hydration errors has been refined, providing clearer logs that indicate mismatches between server-rendered and client-rendered content[1][2].

These features collectively aim to streamline development workflows, enhance performance, and improve the overall user experience in applications built with React.