Definition
A custom dimension registers an event, user or item parameter in Google Analytics 4 so it can be used in reports and explorations.
In practice
GA4 collects event parameters automatically, but most custom parameters only appear in standard reports after they are registered as custom dimensions in Admin.
Registration is not retroactive: reports show values from the moment the dimension is created. Standard properties allow 50 event-scoped and 25 user-scoped custom dimensions.
Good candidates are low-cardinality values that explain behavior, such as plan, form name or button location. High-cardinality values like IDs and timestamps belong in BigQuery instead.
Learn more: GA4 custom dimensions.
Related terms
- Key event (GA4)A key event is a Google Analytics 4 event you mark as important to your business, such as purchase, sign_up or generate_lead.
- Data layerA data layer is a JavaScript array, usually window.dataLayer, that a website uses to pass structured event and page data to Google Tag Manager.
- UTM parametersUTM parameters are tags added to a link, such as utm_source, utm_medium and utm_campaign, that tell analytics tools where a visit came from.
How Markitech helps
Markitech connects your AI to Google Ads, GA4, Google Tag Manager, Meta and 12 more platforms, so it can check how Custom dimension (GA4) is set up in your own accounts and tags and propose fixes. Every change is held until you approve it.