Intent to Extend Experiment: Cookies Having Independent Partitioned State (CHIPS)

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Dylan Cutler

May 25, 2022, 6:52:46 PM5/25/22

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Spec (Copied from I2E)

Summary (Copied from I2E)

Given that Chrome plans on obsoleting unpartitioned third-party cookies, we want to give developers the ability to use cookies in cross-site contexts that are partitioned by top-level site (or First-Party Set, where the site uses that feature) to meet use cases that are not cross-site tracking related (e.g. SaaS embeds, headless CMS, sandbox domains, etc.). In order to do so, we introduce a mechanism to opt-in to having their third-party cookies partitioned by top-level site using a new cookie attribute, Partitioned.

Link to “Intent to Prototype” blink-dev discussion (Copied from I2E)

Goals for experimentation (Copied from I2E)

CHIPS is a new, opt-in technology meant to preserve a set of use cases (e.g. third-party embeds) that may break once third-party cookies are phased out while preventing cross-site tracking. We need to validate whether the proposed syntax and semantics solve these use cases prior to third-party cookie obsoletion by giving developers a way to test it in a scaled manner and provide early feedback. We hope to validate ergonomics, deployability, and backward compatibility.

Experimental timeline (Modified)

The experiment  started in M100 and started on March 29th, 2022 and is currently scheduled to run until June 14, 2022.

We would like to extend the experiment through M104; or in other words, until the release of M105, which is August 30th, 2022.

Any risks when the experiment finishes? (Copied from I2E)

Since Chrome will not send and may delete partitioned cookies when it is started with the feature disabled, sites that set cookies with the Partitioned attribute during the experiment will no longer have those cookies available on clients' machines.

Reasons this experiment is being extended (New)

  • We are talking to multiple interested testing partners, with different use cases, who have requested additional time to prepare for the origin trial, and test the feature.  Extending the trial would allow us to gather more feedback across more use cases.

  • We discovered a bug that prevents Origin Trial opt-in from third-party contexts, which is the typical configuration to use the feature. This bug has been fixed in M103.  

  • We have received feedback that the current origin trial opt-in mechanism is difficult to deploy for large organizations. We have proposed an update to the design of this mechanism, which we aim to release in M103.

Ongoing technical constraints (Copied from I2E)


Debuggability (Copied from I2E)

We have coordinated with the DevTools team to surface cookie partition keys to developers in DevTools. We have added a new cookie inclusion reason with a debug string when sites set Partitioned cookies incorrectly. We may also support surfacing partitioned cookies that are not included in requests because their partition key did not match the top-level site in DevTools.

Will this feature be supported on all five Blink platforms supported by Origin Trials (Windows, Mac, Linux, Chrome OS, and Android)? (Copied from I2E)


Link to entry on the feature dashboard (Copied from I2E)

Mike Taylor

May 26, 2022, 12:47:10 PM5/26/22
to Dylan Cutler,
LGTM to extend to M104 inclusive.

(That brings out the trial to just 5 milestones in total, which is under the 6 milestone limit before renewal requirements kick in:
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Dylan Cutler

Jul 7, 2022, 12:54:33 PM7/7/22
to, Mike Taylor

Hello blink-dev,

I am reaching out to announce some changes to the Cookies Having Independent Partitioned State (CHIPS) origin trial. Starting in Chrome 104, we will be removing the no-Domain requirement for cookies set with the Partitioned attribute. This means that cookies with the Partitioned attribute can now be scoped such that all subdomains on the domain can set and receive the same partitioned cookie. Cookies set with Partitioned still must use the Secure and Path=/ attributes.

We have received feedback from partners telling us that the requirement was making adopting and testing CHIPS more difficult. Therefore, we have decided to remove the requirement for the origin trial to allow developers to test and prepare their sites for the phasing out of unpartitioned third-party cookies in a timely manner. Please note that the change has not been finalized for shipping. The decision on final shipping behavior will be made following further discussion on the explainer issue. Please provide feedback on the linked GitHub issue, or on this thread if this change impacts you.



Dylan Cutler

Jul 14, 2022, 5:03:03 PM7/14/22
to, Mike Taylor
Hello again blink-dev,

I am reaching out to announce that the CHIPS OT has been enabled on 5% of stable users. The rollout will begin today, July 14th 2022.

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