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Attribution Reporting API

This document is an overview of the Attribution Reporting API proposal. The API supports measurement of clicks and views with event-level and aggregate reports.. If you're looking specifically for the explainer for event-level click reports that used to live on this page, head over to Attribution Reporting for Click-Through Measurement instead.


This API is being incubated and developed in the open. Here are ways to participate:

  • 🗓 Join the bi-weekly meetings (every second week). In these calls, participants discuss API design proposals and how the API could support various measurement use cases. You can add topics to the next meeting's agenda at any time. Everyone is welcome to join these discussions⏤only make sure to join the WICG.

Note: If you have implementation questions, for example if you're running an origin trial in Chrome and have technical questions, join the Attribution Reporting mailing list for developers and ask your question. If you have general technical questions on your use case, consider opening an issue on the Privacy Sandbox dev support repository.


The Attribution Reporting API makes it possible to measure when an ad click or view leads to a conversion on an advertiser site, such as a sale or a sign-up. The API doesn't rely on third-party cookies or mechanisms that can be used to identify individual users across sites.

The API enables two types of attribution reports:

  • Event-level reports associate a particular event on the ad side (a click, view or touch) with coarse conversion data. To preserve user privacy, conversion-side data is coarse and noised, reports are not sent immediately, and the number of conversions is limited.
  • Aggregate reports are not tied with a specific event on the ad side. These reports provide richer, higher-fidelity conversion data than event-level reports. A combination of privacy techniques across cryptography, distribution of trust, and differential privacy help reduce the risk of identity joining across sites.

These two report types can be used simultaneously. They're complementary.

API features (proposals)

🕙 Last updated: June 2021

All the features below are proposals under incubation. This list evolves over time.

Event-Level reports (clicks and views)

Attribute cross-site click-through or view-through conversions with reports at a per-event level. See details in the Explainer: event-level reports for views and in the Explainer: event-level reports for clicks.

Implementation status:

Click-through: 🟢 available for experimentation in Chrome. See the origin trial.

View-through: 🟤 not implemented yet (all browsers)

Aggregate reports (clicks and views)

Attribution reports for aggregated conversions (both clicks and views). Complements the event-level reports. See details in the Explainer.

Implementation status: 🟤 not implemented yet (all browsers)

App-to-web (clicks and views)

Attribution reports for web conversions for ad clicks (touches) or views that occurred within an Android app. See details in the Explainer.

Implementation status: 🟤 not implemented yet (all browsers)

Cross-device (clicks and views)

Attribute conversions occurring across distinct devices, i.e. as distinct web browser instances. See details in the Explainer.

Implementation status: 🟤 not implemented yet (all browsers)

External Documentation

API guides and blogposts for this API are listed here.