Tired of your app freezing when filtering big lists or switching tabs? React 18’s useTransition lets you prioritize what feels urgent—and what can wait. Let’s break down exactly what this new hook does and how to use it for seamless experience.
What Is useTransition?
useTransition is a hook that helps React schedule certain state updates as “non-urgent.” Instead of locking up your UI during slow renders, it lets React update high-priority UI elements immediately, while background updates (like filtering, data transforms, or slow components) finish in the background.
How use transition works
- Call const [isPending, startTransition] = useTransition(); in your component.
- Wrap any “slow” state change in startTransition(() => { ... }).
- Use isPending to show a loading state while the transition is running.
useTransition Use Cases with Code Examples
1- Search / Filter Large List
2- Pagination & Navigation
3- View Switching
4- Exposing Pending State In UI
The UI reacts instantly (inputs usable!), while the slow/render-heavy bits update smoothly.
Performance Optimization: Avoiding Blocking UI
Heavy computations or updates (like filtering very large lists, switching complex views, or rendering thousands of items) can freeze your UI if they're treated as urgent.
The magic of useTransition is marking these updates as “non-urgent”—letting React keep your app instantly interactive for typing, clicking, and scrolling, while complex changes happen smoothly in the background. Show loaders with isPending to indicate background work and keep users engaged.
How Transitions Differ From useDeferredValue
- useTransition: Wraps a state update, so both triggering and UI rendering are deferred. The update itself is low-priority.
- useDeferredValue: Delays rendering of a specific value/prop, but lets the update happen immediately. Use when you want the user’s input or navigation to update right away, but can delay showing heavy parts of the UI.
Example:
- Use useTransition to defer updating a filtered list, so typing in a search box always feels instant.
- Use useDeferredValue if you want input to update immediately, but postpone re-rendering a slow child component.
Using useTransition With Suspense and Concurrent Mode
React 18's Concurrent features (enabled by default) let you combine useTransition and Suspense for smoother UI flows.
- Wrap slow-loading components (e.g., network fetches) in <Suspense fallback={...}>.
- Trigger state changes with startTransition so React can prioritise displaying a fallback or maintaining interactivity while new content loads.
Example:
Now, even with slow data or code-splitting, your tabs, lists, and pages won’t stall the UI!
Common Mistakes and Gotchas
- Forgetting memoization: If you don’t wrap heavy children in React.memo or use useMemo, even background transitions might cause full re-renders, defeating the performance boost.
- Triggering transitions inside effects: Always invoke startTransition in event handlers or directly—never inside useEffect.
- Overusing transitions: Don’t wrap every state change! Use only for computationally expensive or non-urgent UI.
- Ignoring accessibility: Don’t hide or delay focus-sensitive UI, especially spinners or critical user feedback, while a transition runs.
- Missing pending cues: Always use isPending to display loading indicators during transitions, so users know an action is running.
Summary
React’s useTransition lets you mark state updates as non-urgent to keep your UI responsive during heavy renders like filtering or pagination. It helps avoid UI blocking by showing a pending state (isPending) while updates finish smoothly in the background. Compared to regular state updates, it prioritises urgent interactions over slower work, resulting in better performance and user experience.
Combined with Suspense and Concurrent Mode, it allows seamless loading and interaction. Avoid common mistakes like overuse or ignoring accessibility to harness its full power.