Constraints on Aggregation Reporting data

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, large enough to be used as a unique identifier.
• 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 or view event).
• Noise is applied to reports in the form of a randomized response. The correct conversion count can be recovered using a script.
• Noise is applied with a 0.0024 (0.24%) probability in the current Chrome code.
• Reports are sent with a delay of between 2 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, large enough to be used as a unique identifier.
• trigger_data (conversion-side information) is up to 3 bits; that is, it should be either 0 or 1.
• Up to 1 conversion can be attributed to a given source (ad click or view event).
• Noise is applied to reports in the form of a randomized response. The correct conversion count can be recovered via a script.
• Noise is applied with a 0.0000025 probability (0.00025%) in the current Chrome code.
• Reports are sent with a delay of between 2 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, let's say:

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 aggregation keys allowed in the source registration is 50. This is also the maximum number of contributions per aggregatable report.
• Noise is applied in the aggregation service.
• Reports are sent with a random delay between 0-1 hours.

# 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 origin} (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.
• Prior to Chrome 108, this limitation was as follows: For a given user, within all unattributed sources—ad clicks or views for which no conversion has been attributed yet—there can be a maximum of 100 different destinations (typically, advertiser sites, or sites where conversions are expected to take place).

# Next steps

For more on the timing of reports, review:

• Report scheduling for event-level reports
• Custom report windows