use the new navigator.userAgentData with fallback to navigator.userAgent

[Erdragh]

Chromium and userAgent

As it seems, Chromium and by extension Chrome, Edge, Brave, Opera, etc. will deprecate userAgent in the near future.

Replacement / new Solution

The new replacement for this will be navigator.userAgentData.

Here are the docs on userAgentData, which is still experimental and not supported by Firefox. As such userAgent should still be used as a fallback, as described here:

https://web.dev/migrate-to-ua-ch/

[tapananand]

It seems Chrome has started rolling out changes for this, are there any plans to make these changes in the near future?

[tapananand]

@faisalman Can you please comment on whether this is being considered or not?

[faisalman]

Partially yes, for browsers that are Chrome-based, I'm considering to also use navigator.userAgentData as a fallback whenever some particular values like device.type or os.name were not found by just simply parsing the legacy navigator.userAgent ..

[tapananand]

@faisalman Thanks for your response! Shouldn't the first try should be to use navigator.userAgentData since that's more structured?

[nberg79]

@faisalman

The changes that will be enacted cause the default user agent string to have some values frozen and some values reduced.

Currently minor version reduction has rolled out (April, 2022) and the Desktop UA reduction is rolling out in a phased approach from October 25th until Feb 7th. Additional information about the current phase can be found here. Following the Desktop UA Reduction we will start rolling out the Mobile UA reduction phase on Feb 7th. 

These changes are being enacted to enhance privacy for end users and to help reduce digital fingerprinting. For use cases that still need the data we have developed User-Agent Client Hints as a new expansion to the Client Hints API enabling developers to access information about a user's browser in a privacy-preserving and ergonomic way. The spirit of the API is that users who need the data take action to ask for it instead of all data being provided passively.

There are two main ways of getting the full user agent values supported by UACH. You can specify your needs via headers or you can use the JS API to query the information you need.

I invite everyone to review the attached centralized information pertaining to the changes. Additionally I would recommend focusing on the JS API section and checking out the JS API demo.

UA-R / UA-CH Quick Start

Education

• What are User Agent Client Hints?
• What happens to the User Agent string?
• Public GitHub: UA-CH Explainer
• Public feedback: Open issues

Timeline

• Full UA-Reduction proposed rollout plan
• Key Dates (As of Jan 6th, 2023) (schedule)
  • Chrome 100 release (Mar 29th, 2022)(Deployed)
    • User Agent Reduction Deprecation Trial launches for instances where a site may need more migration time.
  • Chrome 101 release (Apr 26th, 2022)(Deployed)
    • Minor build version is frozen to 0.0.0 and applies to all page loads on desktop or mobile that are not part of the Reverse Origin Trial.
  • Chrome 107 release (Oct 25th, 2022)(Deploying)
    • Desktop based UA string is fully reduced for all page loads that are not part of the Reverse Origin Trial.
  • Chrome 110 release (Feb 7th, 2023)
    • Android Mobile and Tablet based UA string is fully reduced for all page loads that are not part of the Reverse Origin Trial.

Migration

• Migrating to User Agent Client Hints (Full guide)
• Strategy for navigator.userAgent users (JS API)
• Strategy for Static server-side headers
• Delegating access of your high entropy hints to 3P resources
• Handling critical first request client hints beyond the default set
  • The default set of hints includes the browser name with major version, the platform, and the mobile indicator.

Testing

• Chrome Browser - Please use chrome://flags/#reduce-user-agent
• Chrome Webdriver (Selenium testing, regression testing)
  • --enable-features=ReduceUserAgent
• User-Agent reduction code snippets
• Headers & JS API demo

[tapananand]

@faisalman Thanks for the above commit. I see that we are now falling back to UA-CH as you mentioned. But since we are still first getting the values from the UA string, won't we get wrong results now in some cases? For example, the OS version. Is the recommendation here to not use UA parser for those cases and instead directly use getHighEntropyValues API?

[tapananand]

@faisalman Can you please comment on the above?

[faisalman]

@tapananand for the time being, yes, but I don't rule out the possibility of adding client-hints API into this library in the near future..

[faisalman]

Moving user agent client hints-related issue here: #408