Reasons for discrepancies between old Google Analytics Universal Analytics Properties, and the new Google Analytics 4 Properties

Have you noticed discrepancies between your old Google Analytics Universal Analytics properties, and the new Google Analytics 4 properties? As we delve into the differences between Google Analytics 4 (GA4) and Universal Analytics (UA), it becomes evident that discrepancies in session or user numbers are often attributed to the shift in measurement methods.

There are several reasons why GA4 and UA may report different numbers of sessions or users for the same time period. Some of the main factors are: 

  • GA4 and UA have different settings for session timeout. UA has a default session timeout of 30 minutes, which means that if a user is inactive for more than 30 minutes, a new session will start when they resume activity. GA4 has a default session timeout of 5.5 hours, which means that a user can be inactive for up to 5.5 hours and still be counted as part of the same session. 
  • GA4 and UA have different definitions of sessions and users. For example, UA starts a new session at midnight or when a user encounters a UTM parameter, while GA4 does not. GA4 also counts active users, which are users who have an engaged session or log certain events, while UA counts total users, which are all users who interact with the site. 
  • GA4 and UA have different ways of measuring hits, which are the interactions that are sent to Google Analytics. UA uses pageviews, events, transactions, and social interactions as hits, while GA4 uses events as the only type of hit. Events in GA4 can include pageviews, scrolls, clicks, video plays, conversions, and more. This means that GA4 can collect more data and capture more user behavior than UA. 
  • GA4 and UA have different methods of estimating sessions and users when the data volume is high. UA uses sampling, which means that it analyzes a subset of the data and extrapolates the results to the whole population. GA4 uses modeling, which means that it uses machine learning to fill in the gaps in the data based on historical trends and patterns. This can lead to different levels of accuracy and precision in the reported numbers. 
  • GA4 and UA may have different filters applied to the data. Filters are rules that exclude or modify certain data before it is processed by Google Analytics. For example, you may have a filter that excludes internal traffic from your own IP address or a filter that changes the case of URLs to lowercase. Filters can affect how sessions and users are counted and categorized in both platforms. 

These are some of the main reasons why you may see discrepancies in session or user numbers between GA4 and UA. However, there may be other factors that can affect the data quality and consistency, such as tag implementation, data processing latency, cross-device tracking, cookie consent, and ad blockers. Therefore, it is important to understand how each platform works and what settings and configurations you have in place before comparing metrics across them.