Ad Tech & Ad Ops

Google Privacy Update: Chrome to Phase-Out User Agent Strings

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While publishers are still trying to embrace the impact of the imminent cookie-apocalypse, Google has planned to phase-out user agent strings . In a proposal publicly submitted by Google, the company mentions and describes gradual freeze and unification of these strings.

Since the 90s, webmasters have used UA strings to fingerprint website users. Using this, they made adjustments to their website according to user technical specifications. Publishers often use them to feature tailored content, avoid serving bad impressions, and recognize invalid traffic.

What Is a User Agent String?

User agent strings are pieces of text or metadata that have long been used by ad tech industry players for fingerprinting which aims at identifying and tracking users online. Basically, they provide information regarding a user’s device, version of browser used, operating system, and others. 

For example, a Chrome user agent string on a Windows 10 will appear as:

Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/79.0.3945.130 Safari/537.36

What Is the Update?

User agent strings cannot be removed from Chrome because that might impact performance of old websites that are not being maintained regularly. This is why Google plans on not updating Chrome’s User Agent component with new strings. In the long run, all UA strings will be unified into generic values which will hardly reveal any information about the user.

By this we mean that if a user is visiting your website, a generic value will not be able to tell you if they’re using Windows 10 or Windows 7. Additionally, user device information will also not be available. The only information that a publisher can get is the browser (but not the version) that a visitor is using.

Here’s a tentative plan from Google which describes how they will roll out this update:

VersionEstimated DatePlan of Action
Chrome 81Mid March ‘20Google will deprecate access to ‘navigator.userAgent’. They will start showing warnings in Chrome for pages that use user agent strings.
Chrome 83Early June ‘20Google will stop updating their UA component with new strings, further unifying agent strings across all OS versions.
Chrome 85Mid September ‘20Fingerprinting will be completely nullified. Google will unify desktop OS string as a common value for desktop browsers.

What Publishers and Webmasters Can Do About the Update?

User agent strings helped publishers and developers in enhancing web page display according to user’s device, OS, and browser specification, thus decreasing bounce rate. 

The good news is that while Google is implementing these updates to comply with privacy standards, the online advertising industry can still protect itself. A new replacement mechanism for user agent strings has emerged from Google’s privacy sandbox named as Client Hints. Through Client Hints, website owners can request information about the user. They will get this information only after the browser has approved explicit sharing. This will save webmasters from violating privacy standards in the form of fingerprinting. 


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