What are Client Hints?

Updated at: Jul 2, 2024

A Client Hint is a "HTTP Header" that some web browsers include in the requests they make to websites; each Client Hint header contains a single piece of information about the web browser or device that's making the request, and the website can choose to use this information for various reasons; often to customize the website for the visitor. For example, your browser might send one client hint to indicate that your device is in "Dark Mode", and so the web server would provide styling for the website to make everything look darker to match your personal preference.

One of the major features of the new Client Hints approach, is the moving away from relying on User Agent strings to identify which web browser, version, operating system, and device that the visitor is using. User Agent strings are messy, confusing, and often contain irrelevant or even incorrect fragments of information in them. With Client Hints, the idea is to be accurate and to make it much easier to find that kind of information out.

Client Hints are one of the ways that whatismybrowser.com detects which web browser, operating system, and device you are using.

You can see the Client Hints that your browser is sending if you are curious.