useId hook in React

React’s useId hook provides a unique, stable ID that is useful for accessibility, form inputs, and ensuring consistency across server-side and client-side renders. It was introduced to help developers avoid manually generating IDs, particularly in dynamic or reusable components.

How It Works

useId generates a unique ID string that remains stable across the component’s lifecycle. Unlike using random ID generators, useId ensures that the same ID is used both during server-side rendering (SSR) and client-side rendering (CSR), preventing mismatches.

Example

function FormInput({ label }) {
  const id = useId(); // Generate a unique ID for this component


  return (
    <div>
      <label htmlFor={id}>{label}</label>
      <input id={id} type="text" />
    </div>
  );
}

In this example:

• The useId hook provides a unique id for the input field.
• The <label> is associated with the <input> using the htmlFor attribute, ensuring proper accessibility by screen readers.

When to Use useId

• Forms and Inputs: Use useId to associate <label> and <input> elements with unique IDs for accessibility purposes.
• SSR Consistency: When working with server-side rendered (SSR) applications, useId prevents mismatches between server-generated and client-generated IDs.
• Dynamic and Reusable Components: Ideal for components that are reused or rendered multiple times in a list, ensuring each instance gets a unique identifier.

Limitations

• Single Instance Per Component: Avoid generating too many IDs within a single component, as it can lead to performance issues.
• Not for Global Unique IDs: If you need a globally unique ID, outside the scope of React, useId may not be the best fit.

Conclusion

React’s useId simplifies generating unique IDs in dynamic or reusable components, ensuring consistent IDs across server-side and client-side rendering. It’s especially useful for form inputs, accessibility features, and when dealing with components that are rendered multiple times. By automating the process of creating stable IDs, useId helps prevent common issues with ID collisions and mismatches in modern React applications.