Contact emails

cfred...@chromium.org, johann...@chromium.org, shuu...@chromium.org

Explainer

https://github.com/cfredric/chrome-storage-access-api

https://github.com/privacycg/storage-access/blob/main/README.md

Specification

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

Summary

The Storage Access API provides a means for authenticated cross-site embeds
to check whether they have access to their unpartitioned cookies and
request access to unpartitioned cookies if they are blocked. Chrome already
supports the Storage Access API across sites within the same First-Party
Set, in conformance with the specification, and now we intend to prototype
support for user permission prompts and user-agent-specific permission
behaviors in line with what other browsers are shipping.

Note that Edge previously sent an I2I
<https://groups.google.com/a/chromium.org/g/blink-dev/c/e5fu5Q06ntA/m/UUqPuA8hEQAJ>
for the Storage Access API feature, but we felt it was appropriate to send
a new I2P given that Chrome previously shipped
<https://groups.google.com/a/chromium.org/g/blink-dev/c/V9PzoCvIIIs/m/CZ4JT7YaAgAJ>
support for the Storage Access API gated on First-Party Sets membership and
did not support prompts.

Blink component

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

Motivation

Chrome currently supports the Storage Access API without a user prompt –
access is only granted based on First-Party Sets. However, some user
experiences rely on access to unpartitioned cookies in cross-site contexts
and are not supported by the existing solution. The Storage Access API with
prompts provides a way for sites to request cross-site cookie access to
enable these use cases. We aim to implement this in a way that does not
overwhelm users with prompts or compromise their privacy.


Initial public proposal

https://github.com/whatwg/html/issues/3338

TAG review

https://github.com/w3ctag/design-reviews/issues/807

TAG review status

Positive
<https://github.com/w3ctag/design-reviews/issues/807#issuecomment-1431464692>

Risks

Interoperability and Compatibility

There is minor compatibility risk as Firefox and Safari already differ
slightly in their user-agent-specific prompt requirements. Chrome's planned
behavior is closest to Safari's current behavior, and we aim to standardize
as much of this user-agent-specific behavior as possible over time.

Gecko: Shipping

WebKit: Shipping

Web developers: Positive

There has been great developer interest in the Storage Access API, given
that it provides the only predictable way of working with cross-site
cookies in many browsers. Various developers have chimed in on
https://github.com/whatwg/html/issues/3338 and filed issues on
https://github.com/privacycg/storage-access.

Other signals: Edge has shipped Blink's current implementation of this
behavior, which differs from Chrome's plans. We have kept (and intend to
continue keeping) Edge engineers in the loop about these changes and there
will be feature flags to control this behavior.

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

None


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

No, because prompt behavior and user-agent-specific behaviors are not
testable. The Storage Access API itself is tested at
https://wpt.fyi/results/storage-access-api.

Flag name

StorageAccessAPI, PermissionStorageAccessAPI

Requires code in //chrome?

True

Estimated milestones

Desktop 117

Android 119


Link to entry on the Chrome Platform Status

https://chromestatus.com/feature/5085655327047680

Links to previous Intent discussions

https://groups.google.com/u/1/a/chromium.org/g/blink-dev/c/e5fu5Q06ntA/m/1KF5oNEXAgAJ

https://groups.google.com/u/1/a/chromium.org/g/blink-dev/c/V9PzoCvIIIs/m/b4R9G0xoCQAJ


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

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