Countdown to G-Day: Phase 6 of the User-Agent reduction


1/9/2023 1:30 PM

Google User Agent Client Hints Version 4 Chrome Web

This is a fundamental change that will affect device detection as you know it

The penultimate phase of Google’s User-Agent reduction will roll out in just three weeks – this time, Chrome mobile and tablet User-Agents will change.

Update: Google has provided an update on the Phase 6 User-Agent reduction timeline. Please refer to our Google Q4 report blog for more information.

Get support for this change

Phase 6: reduced device model information in mobile and tablet User-Agents

Phase 6 of the User-Agent reduction begins with Chrome 110 which is due for release on 1 February 2023. It will be the first Chrome version that has information removed from mobile and tablet User-Agents.

The device model and android version information will not be in the Chrome User-Agent.

Google will instead replace this information in the User-Agent with a fixed value. Let's look at an example with a Samsung Galaxy mobile User-Agent. The device model information (SM-A205U) will be replaced with a fixed value of K, and the android version (Android 9) will be replaced with a fixed value of Android 10.

Mobile (user on Samsung Galaxy, for example)
Previous UA Mozilla/5.0 (Linux; Android 9; SM-A205U) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/ Mobile Safari/537.36
Phase 6 UA Mozilla/5.0 (Linux; Android 10; K) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/ Mobile Safari/537.36

In essence, you will not be able to tell the difference between different mobiles devices, whether it’s a Samsung Galaxy S21 or a Huawei Mate 50 Pro. This change on 1 February will affect all mobiles and tablets that are using Chrome 110 and later.

The only way to accurately detect these devices is through User-Agent Client Hints.

User-Agent Client Hints

Google created User-Agent Client Hints (UA-CH), an alternative to the User-Agent HTTP request header. Google gradually introduced UA-CH to their Chrome browser and has now moved to reducing information available within the Chrome User-Agent.

We've blogged extensively every step of the way: from the announcement of User-Agent Client Hints to the different phases of the User-Agent reduction.

The time to act is NOW!

This is the most crucial point in the User-Agent reduction. Chrome dominates the browser share worldwide, making up 65% of the browser share. The changes coming on 1 February will therefore affect 65% of traffic to your websites or products.

If your device detection is not updated for this change, you may see drastic impact to your business. If you use a free, open-source, or internal User-Agent parser, it may no longer work as it does not contain User-Agent Client Hint data. If you rely on the User-Agent within your website, the changes to Chrome may break your site.

You need to ensure you have support for User-Agent Client Hints within your device detection, analytics, products, and websites.

Prepare for the User-Agent reduction

The best way to prepare for the User-Agent reduction is to ensure your web offerings are configured to receive User-Agent Client Hints data.

Version 4.4 of 51Degrees contains full support for UA-CH. Version 3 does not contain support for the User-Agent reduction nor User-Agent Client Hints, so Version 3 customers will need to upgrade to Version 4.4.

If you are a new customer, or a Version 3 customer of ours, you can follow these instructions to get started with 51Degrees. Alternatively, you can get in touch and we'll happily help you out.

Get started with Version 4.4

Google's User-Agent reduction is due to conclude with Chrome 113, scheduled for end of April 2023 – we've been referring to this date as “G-Day”. All page loads using Chrome will receive the reduced User-Agent.

User-Agent reduction phase Date Summary of the changes
Phase 1 September 2021 Chrome 92. Warn about accessing navigator.userAgent, navigator.appVersion, and navigator.platform in DevTools.
Phase 2 October 2021 to March 2022 Chrome 95 to Chrome 100. Launch of reduced User-Agent origin trial for users to provide feedback.
Phase 3 March 2022 Chrome 100. Launch a reverse origin trial (opt in).
Phase 4 April 2022 Chrome 101. Reduction of Chrome version number present in the User-Agent.
Phase 5 October 2022 Chrome 107. Reduction of platform and version information present in desktop User-Agents.
Phase 6 February 2023 Chrome 110. Reduction of device model and Android version information present in Android mobile and tablet User-Agents.
Phase 7 May 2023 Chrome 113. All page loads receive the reduced User-Agent.

This is not a problem that will go away: as more people update to the latest version of Chrome, you need to prepare now before it's too late.