useDeferredValue in React – Importance, Use Cases, and Examples

When working with modern React apps, performance plays a big role. Sometimes components re-render too often and cause lag in your app. React introduced useDeferredValue to solve this problem.

It allows you to defer a changing value until the main updates are finished. Simply put, it makes your app feel smoother to users by delaying some updates when required.

Let’s see why it is important, how it works, and when to use it.

Why useDeferredValue is Important

• It helps avoid expensive re-renders.
• Improves user experience while typing or searching.
• Makes UI updates feel faster even with heavy components.
• Keeps the UI responsive without blocking input.

Practical Use Cases of useDeferredValue

1. Search Input with Large List
   When typing in a search box, the list may be large. useDeferredValue updates the input immediately while the filtered results update with a small delay. Smooth typing, no lag.
2. Real-time Filters
   If you have filters applied on a long data table, useDeferredValue ensures that the dropdown selections are fast while the table updates after.
3. Charts and Visualizations
   When dealing with huge datasets, useDeferredValue can slow down costly rendering tasks but keep the interactions snappy.

Example 1 – Search Box

import React, { useState, useDeferredValue } from "react";

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

  const filtered = items.filter(item =>
    item.toLowerCase().includes(deferredQuery.toLowerCase())
  );

  return (
    <div>
      <input 
        type="text" 
        value={query} 
        onChange={e => setQuery(e.target.value)} 
        placeholder="Search..."
      />
      <ul>
        {filtered.map((item, index) => <li key={index}>{item}</li>)}
      </ul>
    </div>
  );
}

👉 Here, typing stays smooth even if the list is huge.

Example 2 – Large Table with Filters

import React, { useState, useDeferredValue } from "react";

function DataTable({ data }) {
  const [filter, setFilter] = useState("");
  const deferredFilter = useDeferredValue(filter);

  const filtered = data.filter(row => 
    row.name.toLowerCase().includes(deferredFilter.toLowerCase())
  );

  return (
    <div>
      <input 
        type="text" 
        placeholder="Filter by name"
        value={filter} 
        onChange={e => setFilter(e.target.value)} 
      />
      <table>
        <tbody>
          {filtered.map(row => (
            <tr key={row.id}>
              <td>{row.name}</td>
            </tr>
          ))}
        </tbody>
      </table>
    </div>
  );
}

Interview Questions and Answers on useDeferredValue

Q1. What is useDeferredValue in React?
A: It is a React hook that lets you defer value updates to keep the UI responsive.

Q2. How is useDeferredValue different from useTransition?
A: useDeferredValue works on a specific state value to delay updates, while useTransition wraps a state update as non-urgent.

Q3. When should we use useDeferredValue?
A: When rendering is expensive (large lists, tables, charts) and input should stay responsive.

Q4. Does useDeferredValue block UI updates?
A: No, it always updates the input immediately, and only defers the heavy part of updates.

Q5. Can useDeferredValue improve performance in search features?
A: Yes, it helps smooth user typing while delaying heavy list filtering work.

Conclusion

useDeferredValue is a small but powerful performance hook in React. It is especially useful in search, filters, tables, charts, and large data rendering. By applying it in the right places, you can make your React applications faster and more user-friendly.