[blink-dev] Web-Facing Change PSA: Attribution Reporting API remove aggregation key identifier size limit for trigger registrations

[Nan Lin]

Contact emails

akash...@google.com, lin...@chromium.org, john...@chromium.org

Blink component

Internals > AttributionReporting

Summary

Currently the aggregation key identifier length limit (https://wicg.github.io/attribution-reporting-api/#max-length-per-aggregation-key-identifier) is checked in both source and trigger registrations.

As this limit is not for privacy and it's not persisted in the storage, we are removing this limit in trigger registrations. This is consistent with other fields in the trigger registrations, e.g. filters and scopes, whose size is only checked in source registrations, but not trigger registrations.

Explainer/Spec changes

1. Spec: https://github.com/WICG/attribution-reporting-api/pull/1435

Risks

This change introduces slightly different behavior when long aggregation key identifiers (i.e. aggregation keys that exceed the limit) are specified in the trigger registration. Prior to M131, trigger registrations that specify long aggregation key identifiers would be dropped. Starting from M131, those trigger registrations would still be processed for attribution, but the aggregatable trigger data or aggregatable values specified with the long aggregation key identifier would be ignored effectively and not included in the final attribution reports (i.e. if a report is generated for the trigger registration).

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

All except for Android WebView

Is this feature fully tested by web-platform-tests?
No, due to difficulty of adding significant coverage for Attribution Reporting API because of API-mandated delays and noise. However, the feature is covered by comprehensive integration tests (commonly referred to as “interop tests”) that are also reusable by other implementations. 

              

Estimated milestones

This change is anticipated to ship as part of Chrome 131. 

Link to entry on the Chrome Platform Status

https://chromestatus.com/feature/5131578140000256