React 18

React 18 introduces the Concurrent Renderer: a foundational update that unlocks powerful new features, including Automatic Batching and Transitions, for superior application performance and user experience.

This is a major release, focused on delivering the new Concurrent Renderer: a powerful, opt-in mechanism that allows React to interrupt, pause, and resume rendering. Key performance gains come from Automatic Batching, which now groups multiple state updates (even in promises or timeouts) into a single re-render, reducing unnecessary work. Adoption is simple: switch to the new `createRoot` API to enable concurrent features. Developers gain granular control over UI responsiveness using new APIs like `startTransition` (to mark non-urgent updates) and `useDeferredValue` (to defer rendering of non-critical sections), ensuring a smoother user experience.

https://legacy.reactjs.org/blog/2022/03/29/react-v18.html