React Developer interview question · Most asked
What is concurrent rendering in React?
Summary
Concurrent rendering lets React prepare multiple versions of the UI and interrupt, pause or abandon rendering work, so urgent updates (typing, clicks) aren't blocked by expensive, non-urgent renders (filtering a large list, route transitions).
Longer Answer
It's enabled by createRoot and opt-in features: startTransition/useTransition, useDeferredValue and Suspense. Rendering must be pure because React may render components multiple times or discard results.
Key Points
- Interruptible rendering
- Urgent vs transition updates
- Enabled via createRoot + transitions/Suspense
- Requires pure renders
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