Event Tracking in GA4 vs. Universal Analytics

Universal Analytics and classic Google Analytics, events have the following 3 dimensions: eventCategory (required), eventAction (required), eventLabel (optional). They are string types. Events can also have an optional metric: eventValue. It is a numeric type. Events have NO event names.

In GA4, events are the foundation of the GA4 data model. Pageviews and transactions are all treated as events. Events in GA4 are required to have names. They can also have optional “event parameters (names/values)” or “user properties” . The event parameters/user properties can be configured as event-scoped or user scoped “custom dimensions” (for string type values) or “custom metrics” (for numeric type values) in the GA4 portal and show the data in GA4 reports. If you do not configure them as custom dimensions or custom metrics, you will not be able to show the data in GA4 reports.

Here are some important quotas for events:
For standard GA4 properties:

  • 25 event parameters per event
  • 50 event-scoped custom dimensions per property
  • 50 event-scoped custom metrics per property
  • 25 user-scoped custom dimensions per property

For app tracking, there is a limit of 500 distinct event names per app instance (app client/visitor). The limit does not apply to web events.

For big query export: daily export: 1M events; streaming export: unlimited.

See details on Analytics 360 quotas.

As a best practice, you should avoid creating high-cardinality custom dimensions. High-cardinality dimensions are dimensions with more than 500 unique values per day. These dimensions may negatively impact your reports and cause data to aggregate under the (other) row. See details here.

Recommended Events
GA4 has a list of recommended events.

The significance of recommended events is that they are (or may be in future product updates) treated differently in the reporting interface. For example, Google Analytics 4 looks specifically for the recommended online sales events and parameters to populate the built-in Monetization reports.

Properties of GA4 recommended events and auto events also need to set up custom dimensions. If you want visibility into video progress, create a custom dimension based on video_percent. See details.

Universal analytics to GA4

GA4 has the option to automatically map universal analytics events to GA4 events. It maps “event action” to event name, then maps other dimensions and metric in Universal Analytics to GA4 event parameters as following:

‘eventCategory’ -> ‘event_category’
‘eventLabel’ -> ‘event_label’
‘eventValue’ -> ‘value’

Similar to other recommended events and auto events, you need to create custom dimensions/metric for the mapped GA4 event parameters in GA4 to get visibility of them in the GA4 report.

See details here for more information.