Tracking and measurement
Event deduplication
Preventing the same conversion from being counted twice when it is sent by both the browser pixel and the server. Done with a shared event ID.
Event deduplication stops the same conversion from being counted twice when it is sent by two routes, typically the browser pixel and a server-side call. Both carry the same event ID, and the platform keeps one copy. Without it, a store running CAPI and the pixel together reports roughly double the purchases it made.
Deduplication failures are a common cause of ad figures that look too good. Purchase counts rise, cost per purchase falls, and bidding strategies learn from inflated data. The opposite failure also exists: events sent with mismatched IDs are kept as duplicates, while events sent with the same ID but different values can keep the wrong one.
This is worth knowing when an assistant reads ad data, because it cannot see the duplication. A quick check is to compare the platform's purchase count with the store's order count for the same period and attribution window. A large, consistent surplus points at deduplication; a deficit points at blocked or missing events.