[webkit-dev] Request for position: UA-CH API Updates

Mike Taylor miketaylr at chromium.org
Wed May 12 14:05:41 PDT 2021

Hi there WebKit folks,

I'm writing to request a position on some recent API updates to the 
User-Agent Client Hints API.

There's a blink-dev I2P on the topic at [1], but I'll repeat the updates 


**1. Sec-CH-UA-Bitness: adds a new high-entropy hint to expose the OS 
bitness, which may be combined with Sec-CH-UA-Arch to provide optimized 
binaries for download, for example.**


*Spec PR: https://github.com/WICG/ua-client-hints/pull/210. In the 
linked issue Maciej mentioned[2] that were Apple to implement this, it 
may just send the empty string or a fixed value (which are valid values, 
per spec). *


2. Make Sec-CH-UA-Platform a low-entropy hint: OS is passively 
observable at the TCP level anyways, so we plan to change this to be 
low-entropy and send as a default header (similar to Sec-CH-UA and 

Spec PR: https://github.com/WICG/ua-client-hints/pull/221

3. Include low-entropy hints by default in UADataValues (returned by 
getHighEntropyValues()). If a hint moves from high to low-entropy, this 
future proofs any code relying on it.

Spec PR: https://github.com/WICG/ua-client-hints/pull/226

4. Add a toJSON method to NavigatorUAData’s IDL. Technically a bugfix, 
but it is an API change (instead of returning {}, 
JSON.stringify(navigator.userAgentData)) will now be useful)

Spec PR: https://github.com/WICG/ua-client-hints/pull/228


(For context, Maciej provided a review previously in 
and filed a lot of great issues. 2 remain open: issues 151 and 148)




-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.webkit.org/pipermail/webkit-dev/attachments/20210512/0a706615/attachment.htm>

More information about the webkit-dev mailing list