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Facebook CAPI Deduplication and Match Key Parameters

· 4 min read
Aleksandar Vucenovic

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If have ever run into one of the following errors:

  • "Event Missing Some Deduplication Parameters"
  • "Invalid Match Key Parameters"

Then using the Pixel Manager for WooCommerce is the right choice.

What do those errors mean

Facebook uses so called event IDs to deduplicate events that are being sent from the browser and from the server to Facebook.

If those event IDs are missing, or if they don't match, then Facebook can't deduplicate the events and as a consequence reports get inflated.

When Facebook detects irregularities that likely indicate problems with the event IDs, then those errors pop up.

What is Facebook CAPI

After enabling Facebook CAPI the browser pixel and the server are sending common events to Facebook in parallel. That means each add-to-cart event, each purchase event, etc. is sent twice to Facebook. So essentially, every event is duplicated.

The idea behind this method is to ensure that at least one of each duplicated event makes it through to Facebook, in order to increase the likelihood that the event is measured by Facebook. If for example a very old browser is not capable of sending the event through the browser, then in this case the server ensures that Facebook receives the event, and vice versa.

But in those cases where both events, browser and server, get through to Facebook, we don't want Facebook to count every duplicated event two times. For instance the purchase conversion value would get inflated by a factor of two. To avoid duplicated data in the reports Facebook deduplicates browser and server events by comparing the event ID that is being sent with each browser and server event. And here comes the important bit. Those browser and server event IDs have to match exactly. Only then Facebook is able to deduplicate those events.

Common conditions under which missing deduplication parameter or mismatches occur

There are five common conditions when these errors occur:

  1. You recently enabled Facebook CAPI: In that case Facebook mixes up old and new values and throws those errors prematurely. You can dismiss the warning.

  2. Server cache has not been deleted after enabling Facebook CAPI: If the server cache is not deleted after enabling Facebook CAPI, it can happen that the server is sending CAPI events, but the browser is not, because the cached pages don't contain the necessary configuration for Facebook CAPI. The solution is to delete the server cache after enabling Facebook CAPI.

  3. Custom tracking code on the website: You have some custom tracking code on the website which was added to the page templates or through Google Tag Manager. Those codes don't generate the required event IDs. You have to remove those custom tracking scripts and leave the tracking entirely to a plugin like the Pixel Manager for WooCommerce, which handles all requirements correctly.

  4. Facebook event auto tracking is enabled: In the Facebook pixel settings you can enable automatic tracking of events. When this feature is enabled Facebook will try to detect events, such as add-to-cart events, and send them to Facebook. But, they will be missing the correct event ID. Therefore, when this feature is enabled, you will need to disable it and leave the handling to the Pixel Manager for WooCommerce.

event auto tracking

  1. Most tracking plugins don't handle event IDs properly: There are plugins similar to the Pixel Manager for WooCommerce, that don't handle event IDs very well. The Pixel Manager for WooCommerce uses a very robust implementation with which missing event IDs or ID mismatches cannot happen. Switch to the Pixel Manager for WooCommerce, if you want to find out.

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False positives

You might have read, that in some cases Facebook throws "false positive" warnings.

I know, I am nitpicking about the following, but I am a strong believer that using the right definitions and grammar helps avoid misunderstandings.

When a warning is thrown about something that's missing but in fact it is there, then it is by definition a "false negative". Only when a test reveals that something is there, which in fact it is not, then it is a "false positive". Soe in this case apparently the correct match key parameters are missing, but in fact they're not. So by definition that would be a "false negative".

Now having that out of the way, there is one more important information about those "false negatives". "False negatives", warnings about missing deduplication parameters or parameter mismatches, only happen under conditions 1 to 4 in above paragraph. But, if none of those apply in your situation, you should switch to the Pixel Manager for WooCommerce.

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