Intent to Extend Experiment: Cookie Deprecation Label

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John Delaney

Jun 5, 2024, 10:57:30 AMJun 5
to blink-dev

We would like to extend the Cookie Deprecation Label experimental feature being used for Chrome Facilitated Testing.  This feature previously received approval to run through the end of M125 (ending roughly June 10, 2024).  The Facilitated Testing period, however, is scheduled to run through June 30, 2024.

Therefore, we would like to extend Cookie Deprecation Labels for another milestone through M126.  

Contact emails,,



To prepare for the third-party cookie deprecation, it is important to understand the full impact of Chrome’s planned transition from third-party cookies to the Privacy Sandbox Ads APIs.

This experiment exposes a temporary set of APIs which provide access to browser-determined treatment and control groups to support opt-in server side testing of the third-party cookie deprecation.

We are exploring ways to address ecosystem feedback that we should continue supporting labels after 30 June.  We expect to provide more information soon.


Link to “Intent to Experiment” blink-dev discussion


Goals for experimentation

The goal of this experiment is to allow adtechs to evaluate the impact of third party cookie phase out through opt-in server side testing. We expect partners to run experiments downstream from the browser provided treatment and control groups.

Experimental timeline

Previously the feature was approved until M125.  We'd like to extend the experiment by one milestone to M126 so that we can continue to support the Chrome Facilitated Testing period until June 30, 2024. Any experimentation after June 30 will be covered by another Intent.

Any risks when the experiment finishes?

Minimal.  The feature is designed in a way that websites must feature detect for the web API. This feature is also only available for a subset of users.

Reason this experiment is being extended

This feature is necessary to support the ongoing Chrome Facilitated Testing effort.  The Facilitated Testing period is scheduled to complete on June 30, 2024 which is slightly beyond our previous approval for the feature.  Therefore we are requesting to extend the experimental feature access to M126.

Ongoing technical constraints


Will this feature be supported on all five Blink platforms supported by Origin Trials (Windows, Mac, Linux, Chrome OS, and Android)?

No, not supported on webview.

Link to entry on the feature dashboard

Mike Taylor

Jun 6, 2024, 1:00:22 AMJun 6
to John Delaney, blink-dev

LGTM to extend one more milestone (M126).

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John Delaney

Jun 6, 2024, 1:31:02 AMJun 6
to Mike Taylor, blink-dev
Thanks Mike. I should have included this in the original email, but the initial I2E for this feature needed 3 LGTMs as it was a non-standard experiment. Does this extension also require 3?

Thanks again!

Mike Taylor

Jun 6, 2024, 1:59:49 AMJun 6
to John Delaney, blink-dev

I will claim that it doesn't, since it's just for 1 more milestone.

(if other API OWNERS disagree, now is a great time to chime in!)

Daniel Bratell

Jun 6, 2024, 3:34:28 AMJun 6
to Mike Taylor, John Delaney, blink-dev

I agree. One lgtm is enough for this, but thanks to John for raising it.


John Delaney

Jun 27, 2024, 3:28:53 PMJun 27
to blink-dev, Daniel Bratell, blink-dev, Mike Taylor, John Delaney
We would like to clarify that all labels will continue to be available in Chrome 126 after June 30th. We will provide further updates prior to Chrome 127 Stable release in July.

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