“Sessions (event based)” is a metric that Funnel provides when the dimension Event Name and the metric Event Count is included in the connect configuration. “Sessions (event based)” aggregates the Event Count of the Event Name “session_start”, which is an event that Google Analytics 4 provides for all properties.
When compared to the normal Session metric, we have found that “Sessions (event based)” produces a very similar figure, most often within a 0-5% margin. The totals for “Sessions (event based)” in Funnel and “Sessions” you see in the Google Analytics 4 user interface don’t match exactly, but they are very close. Therefore, “Sessions (event based)” is useful in most forms of analysis.
Funnel also provides the metric Sessions (session based) when the dimension Event Name and the metric Sessions are included in the connect configuration. “Sessions (session based)” aggregates sessions of the Event Name “session_start”. This metric will most often be within a 0-3% margin.
What is the challenge with the original Sessions metric?
As you might know, the Google Analytics 4 data model works very differently compared to Universal Analytics. For example, the “Sessions” metric becomes a bit more complicated to work with when exported outside the native Google Analytics 4 interface to a database. This is because Google Analytics 4 is an event-driven analytics platform, and one session typically includes many events.
In most cases, especially if you want to look at granular data, it’s impossible to exactly reproduce the Sessions count you see in Google Analytics 4 in the database. This means that when Event level data together with Sessions is exported from Google Analytics 4 to a database, the aggregated number of Sessions is significantly inflated, sometimes by as much as 5x. This is possible to mitigate by utilising the Event name “session_start” together with the metric Sessions or Event count to create a new custom metric (as explained in the section above).
What can be done if even higher precision is needed
In alternative to using the Funnel derived metrics Sessions (event based) and Sessions (session based), if you need the numbers to match exactly, an additional data source can be setup using only the Sessions metric and nothing else.
The cause of inflated values in the Session metric is typically related to the inclusion of one or many dimensions in the data source configuration. If you remove all dimensions from the data source selection you are more likely to get results that match or are very close to the true Sessions value in Google Analytics 4.