Contact emails

janice...@chromium.org, miketa...@chromium.org

Explainer

None. This is a minor change.

Specification

https://www.rfc-editor.org/rfc/rfc9110#field.user-agent

Summary

User Agent (UA) strings in Chromium have been moving towards reducing or 
freezing information - but until WebKit allows us to implement UA client 
hints, we propose adding the OS bugfix number to the UA, for compatibility 
purposes.


Blink component

Chromium>Mobile>iOSWeb 
<https://bugs.chromium.org/p/chromium/issues/list?q=component:Chromium%3EMobile%3EiOSWeb>

Motivation

The Chrome for iOS User-Agent header only includes the major and minor 
version numbers, while Safari and Firefox for iOS include the major, minor, 
and bugfix numbers. We have received a request from external partners to 
match this pattern, and are aware of at least one platform that relies on 
having an accurate bugfix version number to ensure the latest security 
updates are installed.

UA strings in Chromium have been moving towards reducing or freezing 
information - but until WebKit allows us to implement UA client hints, we 
propose adding the bugfix number to the UA, for compatibility purposes.

In practice:

Before this change: Mozilla/5.0 (iPhone; CPU iPhone OS 17_5 like Mac OS X)

AppleWebKit/602.1.50 (KHTML, like Gecko) CriOS/123.0.2924.75

Mobile/14E5239e Safari/602.1


After this change (note the additional “_1” in the OS version token): 
Mozilla/5.0 (iPhone; CPU iPhone OS 17_5_1 like Mac OS X)

AppleWebKit/602.1.50 (KHTML, like Gecko) CriOS/123.0.2924.75

Mobile/14E5239e Safari/602.1



Initial public proposal

None

TAG review

None - this is a very simple change and aligns us with what other browsers 
are shipping.

TAG review status

Not applicable

Risks

Interoperability and Compatibility

None


Gecko: No signal (Firefox on iOS already follows this pattern)

WebKit: No signal (mobile Safari already follows this pattern)

Web developers: We have received at least one external partner request for 
this change.


WebView application risks

Does this intent deprecate or change behavior of existing APIs, such that 
it has potentially high risk for Android WebView-based applications?

N/A (this is for iOS)


Debuggability

None


Is this feature fully tested by web-platform-tests 
<https://chromium.googlesource.com/chromium/src/+/main/docs/testing/web_platform_tests.md>
?

No

Flag name on chrome://flags

None

Finch feature name

kAddBugFixNumber

Non-finch justification

None

Requires code in //chrome?

False

Tracking bug

https://issues.chromium.org/u/1/issues/350426233

Estimated milestones

No milestones specified


Link to entry on the Chrome Platform Status

https://chromestatus.com/feature/5084885065400320?gate=5184007944536064

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