Constraints on Aggregation Reporting data for Attribution Reporting

Understand the data constraints for source and trigger registration, impact on schedules, as well as reporting limits.

To plan your Attribution Reporting strategy, you'll need to know the constraints enforced by the API, including how much data can be collected for each report.

Event-level reports

The following sections on click and view events describe features and limitations to keep in mind.

Click (navigation source)

  • source_event_id (ad-side information) can be up to 64 bits.
  • trigger_data (conversion-side information) is up to 3 bits; that is, it should be an integer between 0 and 7.
  • Up to 3 conversions can be attributed to a given source　(ad click).
  • Noise is applied to reports in the form of a randomized response. The conversion count can be denoised using a script.
  • Noise is applied with a 0.0024 (0.24%) probability in the current Chrome code　(default setting; noise amount may be different depending on the configuration used).
  • Reports can be sent with a delay of between 1 hour and 30 days; the exact mechanism for views and clicks varies. See details in Report scheduling for event-level reports.

View (event source)

  • source_event_id (ad-side information) can be up to 64 bits.
  • trigger_data (conversion-side information) is up to 1 bit; that is, it should be either 0 or 1.
  • Up to 1 conversion can be attributed to a given source (view event).
  • Noise is applied to reports in the form of a randomized response. The conversion count can be denoised using a script.
  • Noise is applied with a 0.0000025 probability (0.00025%) in the current Chrome code (default setting; noise amount may be different depending on the configuration used).
  • Reports can be sent with a delay of between 1 hour and 30 days; the exact mechanism for views and clicks varies. See details Report scheduling for event-level reports.

Aggregatable reports

The following list describes limitations to keep in mind.

Click (navigation source) and View (event source)

The total values of all the buckets attributed to a source should be at most 65536. For example :

The first conversion for a source is:

"campaignCounts": 32768
"geoValues": 1664

The second conversion for that same source is:

"campaignCounts": 12323
"geoValues": 1664

Note that there can be more conversions.

So, in the example,

total = 32768 + 1664 + 12323 + 1664

Keep in mind that:

  • The total must be under 65536, as mentioned earlier.
  • The maximum number of aggregatable reports per source is 20.
  • The maximum number of contributions per aggregatable report is 20.
  • The maximum trigger registration header size is 250kb.
  • Noise is applied in the aggregation service.
  • Reports are sent with a random delay between 0-10 minutes; reports can be sent instantly with ad tech opt-in.

All reports

  • For a given user, within all unexpired sources, there can be a maximum of 100 different destinations (typically, advertiser sites, or sites where conversions are expected to take place). Unexpired sources are ad clicks or views to which a conversion can still be attributed; that is, for which expiry has not yet been exceeded. In other words, the unique destination limit for attribution sources is covered by unexpired sources, instead of pending sources.
  • 100 attributions per {source site, destination, reporting site} (typically {publisher, advertiser, ad tech}) can be scheduled over 30 days.
  • 100 unique reporting origins (typically ad techs) can register sources per {publisher, advertiser} per 30 days. This counter is incremented for each ad click or view (source event), even those that are not attributed.
  • 10 unique reporting origins (typically ad techs) can send reports per {publisher, advertiser} per 30 days. This counter is incremented for every attributed conversion.

Next steps

For more on the timing of reports, review: