Facebook: The external IDs sent by the server and the pixel do not match

What is the Problem?

A warning message appears due to the inability to deduplicate two pageview events.

“The external IDs sent by the server and the pixel do not match”

Deduplication is essential when both the CAPI and the Pixel are implemented so those two events are recognized as one single event. CAPI serves as a server-to-server solution, while the Pixel is the frontend solution. The purpose of deduplication is to avoid having duplicate events present. Facebook uses the "external_id" parameter to identify and eliminate duplicate events on their end.

What is the Solution?

To resolve the issue, it comes all up to getting the “external_id” right. You can take one of two approaches:

If you deliberately use a Frontend Pixel of Facebook separately from the one JENTIS is offering (or the other way around - having a Server Side CAPI of Facebook seperately), you can either ignore the warning or remove the "external_id" inside the Tags you are using with JENTIS. Please be aware that this means deduplication won’t work, and there will be duplicate events - the different “external_id” lead to duplicate events.
You can provide both, the Frontend Pixel of Facebook together with the Server Side CAPI, with the JENTIS solution. This will ensure that the “external_id” is the same and deduplication will work as expected.

Summary:

The warning message arises from the inability to deduplicate two pageview events sent to Facebook. Deduplication is achieved through the "external_id" parameter, which ensures no duplicate events are present. If the source of the CAPI server to server Tags and the Frontend Pixel is not the same, the “external_id” won’t fit. If this is on purpose, and the warning message is bothersome, you can remove the "external_id" from all Facebook tags. However, doing so will disable deduplication, potentially leading to duplicate events. Another solution would be to use the Frontend Pixel as well as the CAPI serverside solution from JENTIS. Choose the appropriate solution based on your requirements and preferences.