5 tools you need to understand User-Agent Client Hints


10/11/2021 5:00 PM

Client Hints Google User Agent Web

Don’t drag your heels because time is running out to prepare

As the months roll by, we’re getting closer to the potential deprecation of the User-Agent string within Chrome, due to begin in Q2 of 2022. The User-Agent string has been part of our web experience for a long time, so it’s a little sad that we may be parting ways with the HTTP header in favor of User-Agent Client Hints (UA-CH).

The reduction of the UA string could break millions of websites if it is not reduced gradually and website owners do not adjust to the change. The risks associated with ignoring this potential change are too substantial, so, if you rely on UA string data, we urge you to consider future-proofing your options. We’ve already begun to improve our real-time data services to support UA-CH.

To help you plan for the widespread release of User-Agent Client Hints, we've compiled a list of all the tools and resources you need to boost your understanding of these new HTTP request headers.

Get support for User-Agent Client Hints

1: Privacy Sandbox

To prepare for any industry change, you need to know when they are likely to happen. The Privacy Sandbox timeline is essential reading as it informs the rest of the web what changes to expect regarding Chrome. For Client Hints, the changes of interest are the User-Agent Client Hints API (currently launched at scale) and the User-Agent reduction (due to begin with Chrome minor version starting in Q2 of 2022).


Need a refresher on the User-Agent string and all this User-Agent Client Hints talk? is a fantastic resource that discusses both the history of the UA string and the context of why Client Hints were created. It also reviews the new addition to the HTTP header zoo and considers whether Google’s motivations are truly altruistic. A good long read for a comprehensive understanding of User-Agent Client Hints.

3: Official infrastructure draft

For the technical audience, the Client Hints Infrastructure is a draft (at the time of writing) community report that discusses the specification of the infrastructure and its integration with Fetch and HTML. The draft seems to be updated somewhat regularly, so it is a good resource to keep up to date with any technical changes to the infrastructure.

4: Client Hints demonstration page

If you already know about Client Hints and want to see what sort of values they return, our Client Hints page is the tool for you. Using a Chromium-based browser you can request UA-CH headers and a Sec-CH-UA value will be returned.

Note: since UA-CH have only been shipped in Chromium browsers, this test page will only return values if you use a Chromium browser (Google Chrome, Microsoft Edge, or Opera for example). For Firefox, Internet Explorer, or Safari users, UA-CH are not supported in your browser just yet (although that could change in the future if these browsers decide UA-CH are the way forward).

5: User-Agent Clint Hints – Your questions answered

To finish off our list of resources, we’ve got a list of questions you may have on UA-CH answered. If the above resources haven’t quite answered your burning questions, then this guide should help you out. And on the off chance that your question still isn’t answered, drop us an email and we will happily give you the information you need.

Here at 51Degrees, we’re not the biggest fans of User-Agent Client Hints. The UA-CH specification relies on a consistent naming system, which is easier said than done when you have so many device manufacturers at play. And when you consider Google’s position in the AdTech market, are they favoring themselves while making life harder for the competition?

But sometimes, things change despite objections. The reduction of the User-Agent string is not something we are looking forward to, but we must be prepared for these proposed industry changes.

The hand of Google using their dominance to dictate the future of the web.

Our real-time data services have been updated to support User-Agent Client Hints and we will continue to upgrade our services should the landscape change any further. At the time of writing, Client Hints is still labelled as an unofficial draft, so we can expect changes on the horizon.

To get the latest support for User-Agent Client Hints, try our services for free. The time to prepare for the future is now!