Intent to Extend Experiment: Conversion Measurement API (Attribution Reporting API)

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John Delaney

Jul 13, 2021, 11:20:25 AM7/13/21
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Design docs/spec

This is a new API for measuring conversions (e.g. purchases) and attributing them to clicked ads, without using cross-site persistent identifiers like third party cookies.

Link to “Intent to Prototype” blink-dev discussion
Link to “Intent to Experiment” blink-dev discussion

Goals for experimentation
For a continuation of the trial, we still hope to see that the measurement data made available through the API produces comparable results to existing click through measurement solutions on the web.

Experimental timeline
This experiment has been running from M86 -> M91.

We'd like to extend the origin trial for two additional milestones, continuing through M93.

Any risks when the experiment finishes?
This API is only additive and does not affect any existing state. Current conversion measurement solutions will work as expected with and without the API, so we don’t believe there are any risks.

In M92, all web-visible names in the API were modified to reflect changes in the spec/explainer. This mitigates burn in risk as developers will need to update their implementation to continue experimenting. See for more info.

We have previously requested an exception to the .5% page load usage limit for Origin Trials. Page load usage is currently around .53% for the feature, narrowly exceeding the limit.

Reason this experiment is being extended
Chrome 92 exposes a new surface for registering attribution sources through the API which will allow more partners to experiment with the Origin Trial.

Additional features are being added to allow prioritization across different events which should allow for more robust measurement.

Ongoing technical constraints

Will this feature be supported on all five Blink platforms supported by Origin Trials (Windows, Mac, Linux, Chrome OS, and Android)?

Link to entry on the feature dashboard

Mike West

Jul 15, 2021, 4:38:55 AM7/15/21
to John Delaney, blink-dev
LGTM to extend the OT through M93. The API changes you've noted seem like a sufficient guard against burn-in, even though the usage levels are high for an OT.

Now might be a good time to file for a TAG review, if you haven't already, and to get more explicit signals from other vendors as per

Good luck!


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