[webkit-dev] Position on User-Agent Client Hints
mcatanzaro at gnome.org
Thu May 7 16:22:10 PDT 2020
My personal $0.02: I'm mildly supportive of this spec. It's certainly
an improvement on existing HTTP user agent headers. I appreciate that
you worked to incorporate feedback into the spec and considered the
concerns of small browsers.
Is it going to solve all the problems caused by user agent headers? No.
If WebKit implements the spec, we're surely going to eventually need a
quirks list for user agent client hints to decide which websites to lie
to, just like we already have quirks for the user agent header. And as
long as Chrome sends a user agent header that includes the string
"Chrome", it's unlikely we'll be able to get rid of the existing quirks
list. But I think client hints will probably reduce the amount of
websites that *accidentally* break WebKit, by replacing wild west UA
header parsing with well-defined APIs, and adding some GREASE for good
measure. The promise of freezing Chrome's UA header sounds nice, as it
makes quirks easier to maintain. And being able to ration entropy by
revealing details about the platform on an active rather than passive
basis is quite appealing.
The spec attracted some misplaced concern about negative impact to
small browsers, which I've rebutted in . I'm not quite so
enthusiastic about this spec as I was initially, especially after I was
convinced that the GREASE is never going to be enough to remove our
quirks list, but it's certainly not going to *hurt* small browsers.
This spec has received some pretty harsh criticism from the user
tracking industry (some call it the "ad industry"). Not historically a
friend of WebKit, so sounds good to me. ;)
One concern I haven't mentioned elsewhere is that frozen UA header
might encourage deeper levels of fingerprinting than are currently
used, e.g. for ad fraud prevention. caddy has started blocking
WebKitGTK users based on TLS handshake fingerprint (yes, really!) .
If techniques like that take off as a result of this, that could
potentially backfire on us quite badly. But websites could choose to do
such things today anyway, client hints or no, and if so, the solution
will be for us to just try even harder to look more like Chrome.
Seems like a net positive overall. I don't work for Apple and can't say
whether it might be implemented by WebKit.
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