That said, your point about it applying just to the relatively small number
of sites on the RWS list is a good one. I do expect you're right that it'll
be easy to drive down usage and I'd also guess that the vast majority of
usage would be gated by a feature detect, right? Just feels like we'll need
a bit more evidence to demonstrate why we know this will be safe to remove
given the high UseCounter.

Rick

On Fri, Nov 7, 2025 at 1:52 PM Rick Byers <[email protected]> wrote:

> This one seems a bit trickier than RWS itself because we have to reason
> about the risk of code that assumes the API exists. I am supportive of
> deprecation now, but perhaps we should come back to the data after RWS is
> removed and see what the usage severity of breakage is in practice before
> approving removal?
>
> Rick
>
> On Fri, Nov 7, 2025, 12:35 p.m. 'Johann Hofmann' via blink-dev <
> [email protected]> wrote:
>
>> Apologies, I used the wrong Chromestatus link (the original feature
>> status), this one is correct:
>> https://chromestatus.com/feature/5162221567082496
>>
>> On Fri, Nov 7, 2025 at 2:44 PM Johann Hofmann <[email protected]>
>> wrote:
>>
>>> Contact emails
>>>
>>> [email protected], [email protected]
>>>
>>> Explainer
>>>
>>> https://github.com/privacycg/requestStorageAccessFor
>>>
>>> Specification
>>>
>>> https://privacycg.github.io/requestStorageAccessFor/
>>>
>>> Summary
>>>
>>> The requestStorageAccessFor (rSAFor) API is an extension to the Storage
>>> Access API that allows a top-level site to request access to unpartitioned
>>> ("first-party") cookies on behalf of embedded sites. Browsers will have
>>> discretion to grant or deny access, with mechanisms like Related Website
>>> Sets (RWS) membership as a potential signal. This allows for use of the
>>> Storage Access API by top-level sites. Following Chrome's announcement that
>>> the current approach to third-party cookies will be maintained, we are now
>>> planning to deprecate and remove rSAFor, as it is only usable in Chrome to
>>> request storage access between RWS sites. Related Website Sets will also be
>>> deprecated via a separate intent.
>>>
>>> Blink component
>>>
>>> Blink>StorageAccessAPI
>>> <https://bugs.chromium.org/p/chromium/issues/list?q=component:Blink%3EStorageAccessAPI>
>>>
>>> Web Feature ID
>>>
>>> None
>>>
>>> Motivation
>>>
>>> Chrome has announced
>>> <https://privacysandbox.com/news/update-on-plans-for-privacy-sandbox-technologies/>
>>> that the current approach to third-party cookies will be maintained. rSAFor
>>> currently has usage on about 0.95% of page loads
>>> <https://chromestatus.com/metrics/feature/timeline/popularity/4332>,
>>> but any website relying on successful invocation of rSAFor (i.e. the API
>>> returns a promise that resolves) must also have registered a set on the RWS 
>>> GitHub
>>> repository
>>> <https://github.com/GoogleChrome/related-website-sets/blob/main/related_website_sets.JSON>.
>>> Any invocations of rSAFor outside of an RWS currently returns a promise
>>> that is rejected.
>>>
>>> Our metrics suggest that almost all of the usage of rSAFor is from
>>> websites that have registered sets. We will continue to monitor usage and
>>> aim to drive it down prior to removal by proactively informing set owners
>>> of the deprecation timelines and request them to turn down usage.
>>> Additionally, other browser engines have not signaled interest in
>>> implementing the API, obviating any interoperability concerns.
>>>
>>> Debuggability
>>>
>>> N/A
>>>
>>> Requires code in //chrome?
>>>
>>> False
>>>
>>> Estimated milestones
>>>
>>> Deprecate in M144, and target M150 for removal.
>>>
>>> Link to entry on the Chrome Platform Status
>>>
>>> https://chromestatus.com/feature/5122534152863744
>>>
>>> This intent message was generated by Chrome Platform Status
>>> <https://chromestatus.com/>.
>>>
>>> --
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>>
>

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