Meta is not deduplicating your browser and server events
When the pixel and the Conversions API send events that Meta cannot match, your purchases get double-counted or dropped, and optimization degrades. The fix is shared event IDs and consistent parameters.
Signs this is happening to you
- Events Manager warns it is not receiving the same events from browser and server
- Purchase counts in Meta look inflated or erratic
- Both pixel and Conversions API are on, but they are not matching
- Attribution and ROAS look off after enabling the Conversions API
What's usually causing it
- Missing or mismatched event IDsMeta deduplicates using a shared event ID. When the browser and server events use different IDs, or none, it cannot tell they are the same purchase.
- Inconsistent event names or parametersIf the two sides send different event names or values, Meta treats them as separate events.
- Only one side sends the event sometimesIntermittent firing means Meta sometimes has a pair to match and sometimes does not, producing erratic counts.
- Timing gaps between browser and serverEvents arriving too far apart can fall outside the dedup window.
How Mimetic finds it and ships the fix
Mimetic runs a real purchase and inspects both the browser and server events, confirming whether they share the event ID and parameters Meta needs to deduplicate.
- We complete a purchase and capture both the pixel and Conversions API events
- We check whether they share a consistent event ID, name, and value
- We flag the mismatch causing the double-count or drop
- We open the fix as a pull request so the two sides deduplicate cleanly
Meta matches browser and server events by a shared event ID and consistent parameters. Without them, the same purchase is counted twice or lost, which is fixable once you see the gap.
Questions
Why is Meta double-counting my purchases?
Because the browser pixel and the Conversions API are sending the same purchase without a shared event ID, so Meta counts it twice. Mimetic confirms whether your events share the ID needed to deduplicate.
What does Meta use to deduplicate events?
A shared event ID plus consistent event name and parameters across the browser and server events. When those line up, Meta merges the pair; when they do not, you get duplicates or drops.
Can you fix the deduplication setup?
Yes. Mimetic identifies the mismatch and can open the fix as a pull request so the pixel and Conversions API send matching event IDs and parameters, which your team reviews and merges.