How to Generate Unique "id" Attributes That Work With Hydration in React?

When you render your components on the server-side, the following happens:

  1. Initial HTML of your components is generated on the server;
  2. This initial HTML is sent to the client;
  3. The client-side JavaScript "hydrates" the server-generated HTML by attaching event listeners and initializing the necessary React components to make the page interactive.

For "hydration" to work properly, the client HTML output has to be exactly the same as the server HTML. One critical aspect that can cause inconsistencies and disrupt hydration is the generation of unique "id" attributes for HTML elements. If you rely on methods such as using a globally incrementing variable or unique identifier generation functions like Math.random() or uuid, the generated ids may differ between the server and client HTML, leading to issues with hydration.

To overcome this challenge, the useId() hook can be beneficial. By using the useId() hook within your React components, you can generate unique and stable identifiers that remain consistent between the server and client. This ensures proper synchronization during hydration.

Compared to using globally incrementing variables or other identifier generation methods, the useId() hook provides a reliable solution. It generates ids that consistently match between the server and client.

By following this approach and using the useId() hook, you can ensure unique HTML "id" attributes that facilitate successful hydration of React components while maintaining synchronization between the server and client HTML.

This post was published by Daniyal Hamid. Daniyal currently works as the Head of Engineering in Germany and has 20+ years of experience in software engineering, design and marketing. Please show your love and support by sharing this post.