React useDeferredValue — Deferred Search and List Filtering

Deferred Updates with useDeferredValue

useDeferredValue returns a deferred version of a value that lags behind during urgent updates. This keeps the input responsive while the expensive child render catches up in the background.

Search as You Type

function App() {
  const [query, setQuery] = useState("");
  const deferredQuery = useDeferredValue(query);
  const isStale = query !== deferredQuery;

  return (
    <div>
      <input
        value={query}
        onChange={e => setQuery(e.target.value)}
        placeholder="Search..."
      />
      <div style={{ opacity: isStale ? 0.5 : 1, transition: "opacity 0.2s" }}>
        <SearchResults query={deferredQuery} />
      </div>
    </div>
  );
}

How It Differs from Debouncing

Aspect	useDeferredValue	Debouncing
Updates	React-managed, interruptible	Timer-based, fixed delay
Stale indicator	Built-in (compare values)	Manual implementation
Works with Suspense	Yes	No special integration
Device adaptive	Yes (faster on fast devices)	Same delay everywhere

Pairing with React.memo

useDeferredValue works best when the expensive child is wrapped in React.memo. This ensures the child only re-renders when the deferred value actually changes:

const SearchResults = memo(function SearchResults({ query }: { query: string }) {
  const results = useMemo(
    () => allItems.filter(item => item.includes(query)),
    [query]
  );
  return <ul>{results.map(r => <li key={r}>{r}</li>)}</ul>;
});

Initial Value (React 19)

React 19 adds an optional second argument for an initial value during the first render:

const deferredQuery = useDeferredValue(query, ""); // Initial value: ""