What is a GA4 Fallback Property/ Data Stream? How does it help to understand tracking-related issues in complex GA setups?

Jun 13, 2023 | Digital Analytics, GA4, GA4 - Data Quality


What is a GA4 Fallback Property?

A fallback property is a secondary or backup value that is used in case the primary value is missing or invalid. In the context of data quality, having a fallback property is important because it helps to ensure that the data being used is valid and consistent, even when the primary value is missing or incorrect. This can help to prevent errors and improve the overall accuracy and reliability of your data. By having a fallback property, you can provide a backup source of information that can be used to fill in missing or incorrect data, allowing you to maintain high levels of data quality even in challenging situations.

Why should I use a Fallback property or data stream?

This is extremely useful when you have to manage different GA4 properties or Data streams and you’re using a dynamically set Measurement ID for your different GA4 tags. 

In some situations, this property, together with a robust set of alerts on collected data, helped our clients to figure out very fast if some “Traffic routing issues” was happening. Here is a post which can help you to know more about how and why to set alerts in GA4.

Traffic routing issues happen when the traffic is collected by the wrong GA4 data stream. You can have this issue for various reasons but, most likely, it happens because of timing issues in the functions ( or extension in Tealium ) initialising GA4 and setting the GA4 Measurement ID. It can also happen, of course, in the case where you messed up with the setup to dynamically assign the measurement ID

How to use a Fallback property in Tealium?

In case you use Tealium and have dynamically set the Measurement ID using a lookup extension you will notice at the bottom of the extension a “default value” you can assign in case none of the conditions set above to populate the GA ID variable happen

In case you’re using another setup to achieve the conditional assignment for your Measurement ID, you can create an extension scoped “Before load rules”, to constantly set the GA measurement ID to the fallback GA4 measurement ID (a new GA4 property) so that if your code doesn’t initialize the GA Measurement ID assignment you’ll still have the GA fallback ID property collecting traffic otherwise lost.

How to use a Fallback property when the GA Measurement ID assignment happens in code?

If you don’t use any Tag Management System and rely on Ad-Hoc code implementations, a general solution to this issue is difficult to suggest. But generally speaking, you should transmit some default value to your function to use in case the GA ID variable has an undefined or not expected value. We suggest using a Regex to validate the correct Measurement ID format.

The usage of a Fallback Property or datastream can help you to spot issues in your tracking right away and can be one way of increasing weariness about traffic routing issues. If you want to know how to have a reliable and robust tracking system feel free to set up a free 15-minute consultation with us. We’ll be happy to support you!

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