Request for Conversion Measurement OT page load limit exception

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John Delaney

May 27, 2021, 2:55:35 PM5/27/21
to blink-dev

We would like to request an exception to the .5% Origin Trial global page load usage limit for the Conversion Measurement API [1] Origin Trial currently running though M91 in accordance with the policy proposed on:

The Conversion Measurement Origin Trial is being run as a 3P origin trial, and has numerous partners who use both 1P and 3P tokens. We are hoping to increase the subset exclusion group size of this OT from ~10% to ~50%.

Based on chromestatus counters[2], this will surpass the .5% limit.

We think this increase is necessary to facilitate more robust testing of the API. Namely:
  • For sites which generate small numbers of conversions (e.g. <100), it is difficult to have confidence in measurements with only a faction of traffic
  • We have received feedback that partners are seeing differences between data gathered from the API and existing measurement solutions, which larger experiment volumes would give us more confidence in.
Overall, we believe that increased usage will allow us to make stronger comparisons between API and existing measurement solutions than what is currently possible.

As noted in our initial I2E [1], we believe the risk of developers relying on the API over their existing mechanisms to be low due to the many restrictions the API imposes on the data it reports.

The original blink-api-owners-discuss thread can be found at: 


Yoav Weiss

May 27, 2021, 4:24:42 PM5/27/21
to John Delaney, blink-dev
LGTM1 to increase the limits, as outlined in

Specifically, please make sure the overall user exposure is below 20% and the OT doesn't run for more than 2 milestones. Also, please report on a monthly basis with learnings and usage precentages. 

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Daniel Bratell

May 27, 2021, 6:03:37 PM5/27/21
to Yoav Weiss, John Delaney, blink-dev

LGTM2 (with emphasis on all that yoavv said)


Chris Harrelson

May 27, 2021, 6:27:08 PM5/27/21
to Daniel Bratell, Yoav Weiss, John Delaney, blink-dev
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