Why Sessions in GA4 Don’t Match with UA

Google Analytics 4 is one of the most hot topics in the industry for a while. As you know Google sunset Universal Analytics in July 2023 and stop processing data and you had to move your current UA account with its new version in order to maintain website measurement We’re still seeing conflicts and debates on GA4’s new UI, features or data discrepancy between older version. Even reluctantly, we need to get used to GA4 and measure performance accurately on this new platform.

Most of the website owners complaint about the data differences between GA4 and UA or some sort of sharp changes in the number of sessions. To better understand the reasons for this situation, we must first examine the differences between GA4 and UA, then the logic of the session definition between both versions, and finally the average level of difference between the two versions.

GA4 vs. Universal Analytics

First of all, GA4 uses different data schemas from UA and it provides combination of both web and app data. It also comprises one or more data streams under 1 account.

As you see on this comparison, GA4 works based on events while Universal Analytics is based on session count. And they have completely distinctive tracking models and data collection policies. So, we should be careful whilst comparing data in these 2 platforms even if they have the same metric name like “session” or “user”.

Why Session Data Discrepancy Happens

  1. GA4 uses an event-based tracking model, while Universal Analytics uses a session-based tracking model. This means that GA4 tracks individual actions on a website, while Universal Analytics groups actions into sessions.
  2. Session timeout settings in GA4 & UA may not be the same
  3. GA4 has stricter data collection policies. GA4 only tracks users who have opted in to data collection, while Universal Analytics tracks all users by default.
  4. GA4 counts a session in a time period if there were any events from the session in the time period. UA counts a session in the time period when it started.

Concluding Thoughts

We’ve started setting up GA4 accounts in 2022 and if you see 8% to 15% change in the number of sessions between GA4 and Universal Analytics accounts, you don’t need to worry. If you have further detail or question, just let us know.