Intent to Ship: Attribution Reporting Feature: Referrer Policy for Attributionsrc Requests

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Akash Nadan

May 17, 2024, 12:21:53 PMMay 17
to blink-dev
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Attribution Reporting with event-level reports

Attribution Reporting API with Aggregatable Reports

Aggregation Service for the Attribution Reporting API


Blink component

Internals > AttributionReporting


We are landing the following change to the Attribution Reporting API focused on:

  • applying element-level referrer policy for specific html elements

This change is based on ad-tech feedback and so that attributionsrc requests are treated like other subresources on the page.

Currently when the API is called through the use of the attributionsrc attribution as part of various html elements (i.e. <img>, <script>, <a>, or, it ignores the resource-level referrer policy attribute set on the html element.

With this change the attributionsrc request will now apply the same resource-level referrer policy set in the <img>, <script>, <a>, or

This will allow ad-techs more control over whether or not they want to be more or less restrictive regarding the referrer information on their attributionsrc requests.

Explainer/Spec changes
  1. Use referrer policy for background attributionsrc requests 

Interoperability and Compatibility

This feature is not a strictly backwards compatible change because before the change the resource-level policy was ignored, but now it is not ignored. Given this change, the value of the request's referrer header may be different than before. This breakage is unlikely, because it would require an API caller to have a different referrer policy on the document and on the resource, which is unlikely for the Attribution Reporting API.


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

The attribution reporting feature will be supported on all platforms with the exception of  Android WebView

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


Estimated milestones

This feature is anticipated to ship as part of Chrome 126

Link to entry on the Chrome Platform Status

Links to previous Intent discussions

Previous I2S: 

Intent to Ship: Attribution Reporting API

Intent to Ship: Attribution Reporting features M117

Intent to Ship: Attribution Reporting features M118

Intent to Ship: Attribution Reporting features M119

Intent to Ship: Attribution Reporting features M120

Intent to Ship: Attribution Reporting features M121

Intent to Ship: Attribution Reporting features M123

Intent to Ship: Attribution Reporting features M124

Intern to Ship: Attribution Reporting features M125

Domenic Denicola

May 20, 2024, 1:20:04 AMMay 20
to Akash Nadan, blink-dev

This looks like a small, well-considered change that makes the platform more consistent. I agree the compat risks are small.

From what I understand, fields like TAG review and standards-positions for other browsers should be covered by the larger umbrella feature, so we shouldn't block on them. However, I would encourage you to include those fields in future Intents, stating that rationale for omitting the reviews.

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Mike Taylor

May 20, 2024, 9:32:51 AMMay 20
to Domenic Denicola, Akash Nadan, blink-dev

LGTM2 (and yes, please don't emit other info in future intents - it really helps with reviews!)

Chris Harrelson

May 20, 2024, 10:28:11 AMMay 20
to Mike Taylor, Domenic Denicola, Akash Nadan, blink-dev
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