As you migrate from Universal Analytics (also called UA or GA3) to GA4, you are going to be comparing the metrics between the two versions of Google Analytics. Keep in mind that these two versions of Google Analytics have different data models and different ways of calculating various metrics, as a result, the metrics won't match but some of the metrics will have a very small difference while some might be very different.
In this post, I am going to compare the metrics in both versions so that you can have a better understanding of these differences.
Users
In Universal Analytics, there are two User metrics: Total Users, and New Users.
In Google Analytics 4, there are three User metrics: Total Users, Active Users, and New Users.
Active Users, a new metric in GA4, is the total number of users who have engaged session or are new users.
Universal Analytics highlights Total Users (shown as Users) in most reports, whereas GA4 focuses on Active Users (also shown as Users).
So, while the term Users appears the same, the calculation for this metric is different between UA and GA4 since UA is using Total Users and GA4 is using Active Users.
Generally, the numbers in both UA and GA should be very close.
However, the following two reasons can lead to bigger differences in the two metrics.
- The method used to track users. For example, if Google Analytics 4 property might be using User-ID while the Universal Analytics property is using Client ID.
- Filters: UA also can exclude certain users based on view filter settings. In GA4 there are limited settings to exclude users, which could result in different numbers.
Page Views
Page Views in UA are called Views in GA4.
Page view counts should be similar in Both UA and GA4. However, the differences can vary based on any filters you may have set up in Universal Analytics or Google Analytics 4.
Sessions
Sessions in UA and GA4 could be different due to the different methodologies used in the two versions.
In UA if a user crosses midnight then a new session starts. In GA4 the session continues so which can lead to different session counts.
However, if you are using view filters in UA then that will impact the session count as that can potentially filter out some sessions in UA but not in GA since in GA4 there is no concept of view filters in GA4.
Additionally, Google Analytics 4 properties use a statistical estimate of the number of sessions that occurred on your website or app by estimating the number of unique session IDs, while Universal Analytics properties don't estimate the number of sessions.
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Conversions
UA counts only one conversion per session for each goal. So, if a user submits the form twice during the same session, only one conversion will be counted for the “Form Submit” goal.
GA4 counts every instance of the conversion event, even if the same conversion event is recorded multiple times during the same session. So, if a user submits the same form twice during the same session, two conversions will be counted.
Note: Universal Analytics supports five goal types: destination, duration, pages/session, smart goals, and event goals. GA4, in contrast, only supports conversion events. At this time, it is not always possible to use GA4 conversion events to precisely duplicate some UA goal types
Purchases
Web purchase counts should match closely in both UA and GA4.
Session/Traffic-based Acquisition metrics
Many acquisition reports will show you users and sessions. These might have slight differences in Users or Sessions as mentioned above.
Note: GA4 can update attributed conversions for up to 7 days after the conversion is recorded, which can result in different numbers in attribution reports.
Bounce rate
In UA Bounce Rate is calculated as the percentage of single-page sessions in which there was no interaction with the page. For example, if a user visits your website and reads the content, on the first-page user visits, for several minutes, but leaves without clicking on any links or triggering any events being recorded as interaction events, then the session will count as a bounce.
In Google Analytics 4, the Bounce rate is the percentage of sessions that were not engaged sessions. In other words, the Bounce rate is the inverse of the Engagement rate.
An engaged session is a session that lasts 10 seconds or longer, has 1 or more conversion events, or has 2 or more page or screen views. If a user doesn't have an engaged session (that is, they don't meet any of the criteria for an engaged session), then Google Analytics counts the session as a bounce.
Since the way bounce rate is calculated in UA and GA4, this metric is going to be very different and likely lower in GA4 than UA.
Event count
This metric will be very different in the two versions and can’t be compared.
In UA, certain actions can be tracked as Events. While in GA4 every action and interaction is tracked as an event. This is a fundamental difference between the two versions of Google Analytics.
Average Session Duration
In UA the session duration is calculated by taking the sum of all the time difference between two page views or two actions (which could include page views and events). So if a user spends 2 mins on page one and 20 mins on page two and leaves then the session duration will be only 2 mins, the time difference between the two page views.
However, in GA4, every 10 seconds (when your website or app is in view) an event called “engagement” is sent to the backend. Hence when the user leaves after 20 mins, GA4 would have sent 12 engagement hits to the server and would count the last 20 mins as well, so the session duration will be 22 mins.
The difference in how these metrics are calculated in the two versions of Google Analytics will cause the difference in these metrics.
Page View Per Session
Pages per session in UA are replaced by Views Per Session in GA4.
Page views per session can be different if the session count is different (see above).
In addition to session-based metrics, there is also a metric called Views Per User in GA4.
Unique Page Views in UA is no longer in GA4
This metrics calculated the number of unique sessions that visited a particular page. This metric is explained in the detail in another post that you should check out.
Unique Pageviews v/s Sessions in GA4
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