Understanding Google Analytics 4 Sessions

Comparing Google Analytics 4 sessions to Universal Analytics (GA3) sessions is the best way to understand them.
Understanding Google Analytics 4 Sessions

Key differences between GA4 sessions and GA3 (Universal Analytics) sessions

#1: In GA3, a session is a group of hits recorded for a user over a particular amount of time. Whereas in GA4, a session is a group of events recorded for a user over a particular amount of time.

#2: Both GA3 and GA4 define a user as an individual who engages on your website or mobile app in one or more sessions.

These actions could be like viewing a page, scrolling a page, clicking on add to cart button, making a purchase etc.

#3: A user can generate one or more sessions in a single day or over a period of time that may extend over a few days, weeks, or even months. As a result, the session counts in your GA3/GA4 property are likely to be higher than the user counts.

NOTE: Unlike in GA3, the user activity is detected automatically in GA4. This may lead to higher active user counts for GA4.

#4: Both GA4 and GA3 sessions can be categorized into “WEB Sessions” and “APP Sessions”.

#5: A “Web Session” starts as soon as a user views a page and no previous session is currently active, both in GA4 and GA3.

#6: A “APP Session” starts when a user either opens your app in the foreground or views a screen, and no previous session is currently active, both in GA4 and GA3.

#7: Since a GA3 session starts as soon as a user views a page, the GA3 session is almost always a session with a page view.

Whereas a GA4 session can start with or without a pageview.

For example, a GA4 session can start with user engagement. So you could end up with views or user engagements with no sessions.

Let’s consider the following scenario,

A user landed on your website but immediately navigates to another browser tab. After a couple of hours, he returns to your website, engages with the content, and then closed the tab.

In this scenario, GA3 will likely count as one session with a pageview.

However, GA4 would count as two sessions. One session with pageviews and one session with user engagement.

The session with user engagement started when the user returned to your website hours later and started engaging with the content.

Because of this, GA4 sessions do not accurately reflect user engagement, and you would be better off focusing on users and events.

#8: The session duration of a GA3 session is calculated as the time elapsed between the first and last hit in the session. Whereas the duration of a GA4 session is calculated as the time elapsed between the first and last event in the session.

#9: In GA3, by default, a session expires if no new hit is sent to the GA server within 30 minutes from when the last hit was sent. It is known as “User Inactivity” during this time when no new hits are sent.

Similarly, in GA4 a session expires if no new event is sent to the GA server within 30 minutes from the time when the last event was sent.

#10: Unlike in GA3, the GA4 property reports on ‘Engaged Sessions’ and ‘Engaged Sessions Per user’.

GA4 defines an “Engaged Session” as the one that,

  • Lasted 10 seconds or longer or
  • Had one or more conversion events fired or
  • Had two or more page views.

GA4 defines ‘Engaged Sessions per User’ as the number of engaged sessions / the number of users.

#11: GA3 counts sessions by counting the sessions metric. Whereas GA4 counts sessions by counting session_start events.

Given that GA3 and GA4’s session counts are computed and adjusted in different ways, they are unlikely to match.