Contact emails

sled...@google.com, johann...@chromium.org, cfred...@chromium.org

Explainer

https://github.com/privacycg/storage-access-headers

Specification

https://privacycg.github.io/storage-access-headers

Summary

Storage Access Headers offer an alternate way for authenticated embeds to 
opt in to unpartitioned cookies. These headers indicate whether embedded 
resources should load with permission they have already been granted, 
reducing loads and latency overall for these use cases.


Blink component

Blink>StorageAccessAPI 
<https://bugs.chromium.org/p/chromium/issues/list?q=component:Blink%3EStorageAccessAPI>

Search tags

storage access api 
<https://chromestatus.com/features#tags:storage%20access%20api>, storage 
access headers 
<https://chromestatus.com/features#tags:storage%20access%20headers>

TAG review

https://github.com/w3ctag/design-reviews/issues/982.

TAG review status

Satisfied in early design review. TAG didn’t expect to have major input on 
the spec and invited us to proceed without their spec review. 

Chromium Trial Name

StorageAccessHeader

Origin Trial documentation link

https://github.com/cfredric/storage-access-headers

Risks

Interoperability and Compatibility

This feature poses a minor compatibility risk, since the Origin header is 
now included on requests that include the "Sec-Fetch-Storage-Access: 
inactive" header - and some servers do not yet properly handle the Origin 
header.

However, this risk is low, because:

* The "inactive" header is only included on clients that already block 
third-party cookies.

* The presence of the "inactive" header implies that the request is 
cross-site, and that the site in question already uses the Storage Access 
API (which is relatively new to the web platform) or that the context is an 
"A > B > A" embedding scenario.

* This feature omits the Origin header from requests whose `credentials` 
mode is not "include".


Gecko: No signal (https://github.com/mozilla/standards-positions/issues/1084
)

WebKit: No signal (https://github.com/WebKit/standards-positions/issues/412)

Web developers: Positive (
https://github.com/privacycg/storage-access/issues/130) Other feature 
requests: * https://github.com/privacycg/storage-access/issues/170 * 
https://github.com/privacycg/storage-access/issues/189

Other signals:

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?

None


Debuggability

This is debuggable via DevTools and via chrome://net-export.


Will this feature be supported on all six Blink platforms (Windows, Mac, 
Linux, ChromeOS, Android, and Android WebView)?

No

The Storage Access API itself is not yet supported on Android WebView.


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

Yes

DevTrial instructions

https://developers.google.com/privacy-sandbox/blog/storage-access-api-headers-logic

Flag name on chrome://flags

storage-access-headers

Finch feature name

StorageAccessHeaders

Requires code in //chrome?

False

Tracking bug

https://b.corp.google.com/issues/329698698

Launch bug

https://launch.corp.google.com/launch/4309903

Measurement

We've written metrics to track the usages of the "load" and "retry" 
response headers, and to measure the incidences of each variant of the 
request header.

Sample links

https://storage-access-headers-demo.glitch.me

Estimated milestones

Origin trial desktop first

130

Origin trial desktop last

135

Origin trial Android first

130

Origin trial Android last

135


Anticipated spec changes

Open questions about a feature may be a source of future web compatibility 
or interoperability issues. Please list open issues (e.g. links to known 
github issues in the project for the feature specification) whose 
resolution may introduce web compat/interop risk (e.g., changing to naming 
or structure of the API in a non-backward-compatible way).

None

Anticipated implementation changes

We decided not to separately integrate the “Activate-Storage-Access” header 
with the SAA Permissions Policy in this initial version. The follow-up work 
to figure out the integration is tracked in https://crbug.com/382291442. 
Because of how SAH works this header already “benefits” from the SAA PP by 
default (SAH won’t work if there’s no SAA permission grant), and we haven’t 
seen developer demand for being able to prevent just the header, but not 
SAA itself. The implementation carries a surprising amount of architectural 
complexity, but we do plan to follow up with this for completeness. Most 
importantly, adding this later is unlikely to cause compat risks because 
SAA has a “*” default allow-list, so we won't be changing default behavior.

Link to entry on the Chrome Platform Status

https://chromestatus.com/feature/6146353156849664?gate=6138146145435648

Links to previous Intent discussions

Intent to Prototype: 
https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CABa1CXyMJzMmpQkZMwQUFGK8-f%3DEerhR2VQbTZephdmE22W%2ByA%40mail.gmail.com

Intent to Experiment: 
https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CABa1CXyYbxwh%3DPdnigTW80d9jez_835R1SV1bQPDjvk1ra5G4g%40mail.gmail.com


This intent message was generated by Chrome Platform Status 
<https://chromestatus.com/>.

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