useDeferredValue Explained

useDeferredValue is a React concurrent hook that lets you delay rendering of non-urgent values so your UI stays responsive.

🧩 What Problem Does useDeferredValue Solve?

It helps prevent UI lag when rendering is expensive but user input must remain fast.

⚙️ Basic Usage

import { useDeferredValue, useState } from "react";

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

  return (
    <>
      <input value={query} onChange={(e) => setQuery(e.target.value)} />
      <Results query={deferredQuery} />
    </>
  );
}

🧠 Mental Model

• query updates immediately
• deferredQuery updates when React has time

🔍 How It Works Under the Hood

• Deferred updates are marked low priority
• Urgent updates interrupt them
• Intermediate renders may be skipped

⚡ useDeferredValue vs useTransition

🧱 Example: Filtering a Large List

const deferredFilter = useDeferredValue(filter);

⚠️ Notes

• Not a debounce
• Requires React 18+
• Delays rendering, not state

✅ Summary

useDeferredValue improves UX by prioritizing urgent updates and deferring expensive rendering.