Facebook ads duplicate conversions: causes and how to de-duplicate
Troubleshooting guide · 2 min read · Updated 2026-10-21 · By the Cofoundr team
Duplicates usually appear when the same event is sent from both the browser pixel and the Conversions API without a shared event ID and event name, so Meta cannot tell they are one action. Send the same event ID and name with both, then check in Events Manager that the duplicates are being merged.
Counting the same sale twice flatters reports and confuses optimisation, and it makes the numbers disagree with the store. The cause is almost always a setup issue, and it is fixable. Meta's rules for de-duplication are described in its documentation, which you should check for the current details.
How duplicates happen
- The pixel and the server both send a purchase, with no matching event ID.
- A thank-you page can fire the event again on refresh or on a revisit.
- Two pixels or two tags on the same site both fire.
- A plugin and a manual install are both active.
How de-duplication works
When you send the same event from the browser and the server, give both the same event name and the same event ID. Meta uses that pair to treat them as one event. Without the ID, they can be counted separately.
How to find duplicates
- In Events Manager, compare browser and server counts for the same event over the same days.
- Use the test events tool, and do one test purchase to see how many events arrive.
- Compare Meta's count with your store's orders, over a full week.
How to fix them
- Generate one event ID per action, such as the order number, and send it with both sources.
- Stop the thank-you page firing again on refresh, for example by firing only once per order.
- Remove extra tags and plugins so only one pixel setup remains.
- Re-test after each change.
A quick note on reporting
Duplicates inflate results and make cost per result look better than it is. If a new client's numbers look too good, check this before celebrating. See conversion tracking not matching.
How Cofoundr helps
Cofoundr cannot see your tag setup, but it reads the figures Meta reports, and the client page shows purchases, revenue and return on ad spend beside the per-ad-set result. A return on ad spend far above what the store shows is a prompt to check for duplicates.
Frequently asked questions
Why does Meta show double my sales?
The most common cause is sending the same purchase from the browser and the server without a shared event ID and event name. Add matching IDs and re-test.
How does Meta de-duplicate events?
It uses the event name and event ID sent from both sources. Check Meta's current documentation for the details.
Will fixing duplicates hurt my results?
Reported results may fall, because the old numbers were inflated. Optimisation usually benefits from cleaner data.