What is useId in React: Unique ID Hook Explained

useId is a React hook that generates a unique ID string for components. It helps avoid ID conflicts in the DOM, especially when rendering multiple instances or during server-side rendering.

How It Works

useId creates a unique identifier that stays consistent across renders. Think of it like giving each component a name tag that no one else has, so you can safely link labels to inputs or elements without mix-ups.

This is especially useful when you have many copies of the same component on a page. The hook ensures each copy gets its own unique ID, avoiding confusion for browsers and assistive technologies.

It also works well with server-side rendering by generating IDs that match on both server and client, preventing mismatches that can cause errors or warnings.

Example

This example shows how to use useId to link a label to an input field with a unique ID.

jsx

import React, { useId } from 'react';

function TextInput() {
  const id = useId();
  return (
    <div>
      <label htmlFor={id}>Name:</label>
      <input id={id} type="text" />
    </div>
  );
}

export default function App() {
  return (
    <>
      <TextInput />
      <TextInput />
    </>
  );
}

Output

<label for=":r0:">Name:</label><input id=":r0:" type="text" />
<label for=":r1:">Name:</label><input id=":r1:" type="text" />

When to Use

Use useId when you need stable, unique IDs inside React components, especially for accessibility features like linking labels to inputs or associating elements with ARIA attributes.

It's helpful when rendering multiple copies of the same component or when your app uses server-side rendering to avoid ID mismatches between server and client.

For example, form libraries, custom input components, or any UI elements that require unique IDs should use useId to prevent conflicts.

Key Points

• useId generates unique, stable IDs for React components.
• It prevents ID collisions when rendering multiple instances.
• Works well with server-side rendering to avoid mismatches.
• Commonly used for accessibility linking like labels and ARIA attributes.
• Introduced in React 18 as a modern solution for unique IDs.

Key Takeaways

useId creates unique IDs to avoid conflicts in the DOM.

It ensures consistent IDs across server and client rendering.

Use it to link labels and inputs for better accessibility.

Ideal for components rendered multiple times on the same page.

Introduced in React 18 as the recommended way to generate IDs.