GA4 is dramatically different than UA for numerous reasons and we highly recommend everyone start to familiarize yourself with those differences as the migration date rapidly approaches. Below are a few important changes we want to highlight since they will have a noticeable impact on how you use and understand GA4 vs UA.

Filters

  • At this time, GA4 does not offer offer you the ability to add custom filters like you can in Universal Analytics.
  • If there are certain types of traffic that you want to include/exclude, force things to be lowercase or uppercase, remove query parameters, you cannot do this.
  • Due to this limitation, you are going to see different metrics in GA4 than you will in Universal Analytics (on top of there being a different data model). 
  • Still no update from Google around this and if they will be expanding filtering capabilities or not by July 2023.  

Views

  • In Universal Analytics, you could create Views - a subset of a Property that can have its own unique configuration settings. 
  • There are no Views in GA4, which makes it more challenging to track specific experiences and parts of your website. 
  • If you have GA360, you can create sub-properties which work the same way as Views, but again, these can only be created if you are paying for GA.

Cardinality

  • The total number of unique values for a dimension is known as its cardinality. If you have ever noticed (other) entries in reporting, this means you are looking at a high cardinality dimension and have run into analytics system limits causing this to happen.
  • In GA3, cardinality generally only occurred if you pulled a report where the dimensions you used had more than 50,000 unique names.
  • In GA4, it works very differently. If you have dimensions with lots of unique values, it can cause EVERY dimension to be aggregated meaning you are much more likely to see (other) entries in reporting.
  • Unless you are exporting your data to BigQuery where you have access to all raw data, this is going to make analysis challenging to do directly in the UI since there is no way to see what is bucketed in (other) and no way to get it out. 

Users

  • The user count you see in UA represents the total number of users detected on your site, regardless if they were active or not. 
  • GA4 focuses on Active Users (shown as Users) - users who actually did something / engaged with your site. 
  • 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. 
  • There is a 'Total User' dimension available to use if you ever want to look at total users vs just active ones.

Session Behavior

  • In UA, a session will break anytime new campaign parameters are detected.
  • In GA4, a session will not break even if new campaign parameters are detected.
    • This is because GA4 is really focusing on a users original acquisition source. 
  • Both GA4 and UA will start a new session if a user comes back after the previous session ended (30 minutes of inactivity)
    • GA4 will only capture new campaign parameters if a user comes back to the site after their original session ended. 
  • Because GA4 will not break a session even if new campaign parameters are detected, you are going to see very different acquisition metrics than what you see in UA. Because of this behavior, the way we track campaign performance is going to have to change.