React 18 Released: Concurrent Features Explained

React 18 is GA. The headline feature is Concurrent Rendering, enabled by the new createRoot API.

Automatic Batching

Previously, state updates inside setTimeout or fetch callbacks were NOT batched. React 18 batches them automatically.

// React 17: 2 re-renders
// React 18: 1 re-render (batched!)
fetch('/api').then(() => {
  setLoading(false);
  setData(result);
});

Suspense for Data Fetching

Combine with libraries like React Query or Relay to show loading states declaratively.