Intent to Prototype: Third-Party Cookie Phaseout

[Johann Hofmann]

Contact emails

joha...@chromium.org, wande...@chromium.org, dylan...@chromium.org, john...@chromium.org 

Specification

None

Summary

This intent is for implementing the changes in Blink that are necessary to perform a controlled rollout and testing of the planned upcoming third-party cookie deprecation, to measure and mitigate ecosystem and user impact. As announced before, we will provide two periods of testing (Mode A and Mode B) for sites to preview and test the lack of third-party cookies.

Before actually deprecating / removing access to third-party cookies, we will send an “Intent to Deprecate and Remove” with additional details to satisfy the Blink launch process requirements.

For more information on Privacy Sandbox for the Web and Google’s plans to phase out third-party cookies, see https://privacysandbox.com/open-web/.

Blink component

Internals>Network>Cookies

TAG review

None

TAG review status

Not applicable

Risks

Interoperability and Compatibility

Because of its ecosystem impact, third-party cookie deprecation has been the focus of the Privacy Sandbox effort which includes various proposals to provide replacement technologies, which are now either shipping already, or currently rolling out. We will share additional information about the state of interop and compat in our Intent to Deprecate and Remove.

Debuggability

None

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

All except WebView, at this stage

Is this feature fully tested by web-platform-tests?

No

Flag name

TestThirdPartyCookiePhaseout

Requires code in //chrome?

Yes, some of the infrastructure that supports rollout and testing needs Chrome code. Embedders can of course still disable 3PCs without this code.

Estimated milestones

Initial phase of Deprecation (1%) is planned for Q1 2024, see https://privacysandbox.com/open-web/#the-privacy-sandbox-timeline.

Link to entry on the Chrome Platform Status

https://chromestatus.com/feature/5133113939722240 

[Ben Kelly]

Please see this blog post discussing how sites can prepare for third-party cookie phaseout:

https://developer.chrome.com/blog/cookie-countdown-2023oct/

In particular, see this note regarding a deprecation trial:

https://developer.chrome.com/blog/cookie-countdown-2023oct/#request-additional-time-with-the-third-party-deprecation-trial-for-non-advertising-use-cases