A Google Analytics 4 custom dimension scope determines how your data is collected.
There are two types: Event scope and User scope.
Before creating a custom dimension, you should be aware of the limits per property. If you have a 360 account, you’ll have higher limits than with a standard Google Analytics 4 account.
GA4 Event Scope Custom Dimensions
To see data from an event parameter in your dashboard, you must create a Google Analytics 4 custom dimension with an event scope.
Google already includes custom dimensions based on many of its automatically collected and enhanced measurement events. If what you want to track something isn’t already a parameter, it may be time to create a custom dimension with an event scope.
Choose event scope instead of user scope if you’re tracking something whose value could frequently change.
For example, if you include word_count as a parameter for blog content, that would fall under event scope. You would then be able to analyze user behavior based on article length.
You would do this because word count is associated with an event, not a user. It’s also likely to change frequently over time.
GA4 User Scope Custom Dimensions
To see data related to a user property, you must first create a custom dimension with user scope.
Google already collects data regarding many user dimensions. These include age, browser, country, language and more.
Before creating a custom dimension with a user scope, make sure the data you want to collect isn’t already tracked.
You would choose user scope for a user property that’s not likely to change often over time.
For example, whether or not someone is a paid subscriber to a news website would fall under user scope. The parameter could be subscriber_status and the values could be paid and free.
That makes sense because this is a data attribute associated with a user, not an event. It’s also unlikely to vary often.