Deduplication Failing in Meta – Event ID Problem

Facebook Conversion API
1

Hi,

We’re seeing a significant discrepancy between lead conversions reported by Meta and actual submissions recorded in ActiveCampaign — sometimes off by as much as 30% to 80%.

In Events Manager, only about 35% of browser events include an event_id, while 100% of server events do. Despite this, Meta shows 0% deduplication via event ID.

So it must be a deduplication issue.

In GTM, both browser and server events are configured to use the same unique event_id, and testing confirms they match. My one theory is that a timing gap between the browser and server event firing could be too large for Meta to deduplicate them correctly.

If timing is a factor, what’s the best way to log and compare the firing times of browser vs. server events?

Also open to any other ideas on what might be causing this issue.

Thanks in advance.

2

Time gap can not be an issue, the dedupe window is at least 12 hr, if not 24 (don’t remember the particulars).

Are you certain all your (client-side) events originate from your setup? If only 35% hold event_id in the first place I would look for parallel reporting sources.

3

Good to know we can rule out the time gap as a hypothesis.

This is a custom event I created specifically for this setup - it doesn’t exist anywhere else.

What else could I latch onto for troubleshooting?

4

Hello, I have pretty much the same problem. Were you able to solve your issue? And if so, what was the problem?

5

This may indicate that your browser events are being triggered not only from your GTM, but also from other places where event_id is not added to the event.
This could be a Meta code snippet in the website code / the work of a plugin or integration / custom events in the Meta event setup tool.

7

I created this custom event specifically for this setup. I double-checked to see if it was triggered outside GTM, but no luck..

8

Not yet, unfortunately

9

what is the ratio of web to server events? I mean in terms of quantity, no event_id

10

For every browser event, we receive about 0.94 server events.

11

A healthy setup will have more server events than browser ones, or they at least would be equal. If you have more browser events - that indicates either a) extra source of reporting on the web or b) not all cases are covered by the server-side setup