Attribution Reporting Feature: Remove Aggregatable report limit when trigger context ID is non-null

concepts

1. Removed Report Limit

   Removes the aggregatable report cap when trigger_context_id is set. Enables per-conversion aggregation without per-source budget juggling.

2. Per-conversion stream

   The high-volume conversion case: large carts where the 20-per-source cap silently dropped events. Side-by-side backend-backed comparison of with vs. without trigger_context_id.

3. Trigger Volume Probe

   Slide conversion count + source count; watch the histogram and dropped-event counter flip between pre-v134 cap and the v134 trigger_context_id-lifted regime.

4. Trigger Context ID Builder

   Build a trigger registration JSON with trigger_context_id on and off. Set conversion count and watch the sent vs. dropped bar comparison flip between the 20-report cap and unlimited mode.

5. Source & Trigger Registration Pair

   Both halves of the attribution loop side by side: the publisher’s Attribution-Reporting-Register-Source (where the cap lives) and the advertiser’s Attribution-Reporting-Register-Trigger (where trigger_context_id lifts it). Edit either header and watch the outcome change live.

6. Mixed-mode adoption

   Real campaigns migrate gradually. Slide the mix percentage from 0% to 100% and watch how partial trigger_context_id adoption delivers a proportional uplift — the triggers that carry it are unlimited, the rest still hit the cap.

why it shipped

This change is based on API caller feedback and the need for being able to measure a higher number of conversion events for certain user flows.

references

• ChromeStatus entry