Attribution-Reporting API: Remove aggregation key identifier size limit for trigger registrations

concepts

1. Remove key size limit

   Drops the aggregation key identifier size limit for triggers in Attribution Reporting. Larger / richer key namespaces possible.

2. Source vs trigger asymmetry

   Type a key and watch both sides verdict it: triggers accept any length, sources still cap at 25 because they're persisted in browser storage.

3. Trigger payload builder

   Compose a real trigger payload: arbitrary-length descriptive key names mapped to integer values, with live duplicate, empty-key, key-piece, and contribution-budget validation.

4. Source vs trigger header explorer

   Side-by-side: the two ARA response headers as the server would emit them. Where the cap still applies and where it doesn't.

why it shipped

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 f

references

• ChromeStatus entry
• Spec