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Custom Dimensions
After setting up priority conversions and core GA4 events, continue to migrate your key customizations, such as custom dimensions to maintain current functionality and data capture.
Key Tasks
- Map UA dimensions and metrics to GA4’s built-in parameters.
- Choose event-scoped and user-scoped dimensions as needed.
- Create a custom dimension.
- Create a custom metric.
Custom Definitions UI
Overview
Dimensions and metrics create the categories and value schema for data throughout GA reports and explorations, providing the nomenclature and structure to help transform raw data into analytic insights. While built-in GA4 dimensions and metrics span many usage categories, custom dimensions and metrics extend the dataset further. Creating reusable dimensions and metrics allows GA to capture additional information about events and users that are relevant to your business.
Mapping UA Custom Dimensions and Metrics
If a UA implementation used customization to capture non-standard event parameters, you will likely need to create custom dimensions (and metrics) in GA4. Any time a custom parameter is used in GA4, a dimension must be made available for GA4 to access. However, before creating new custom dimensions, first verify that the parameter needed is unavailable in GA4. A full table of pre-built dimensions is available in GA support. While some require configuration, many are pre-populated once the Google tag or Google Analytics for Firebase (GA4F) SDK is added to your property.
For example, a list of ecommerce dimensions with definitions and usage descriptions is available and recommended for use when migrating online sales events and parameters. In addition, some general parameters have been added that previously required customization in UA.
You don't need to set up custom dimensions and metrics for data collected through automatically collected events, enhanced measurement, and recommended events.
To map your UA parameters, review the relevant categorized table sections (e.g., “General,” “Demographics,” “Video”) or expand the full table set and search the article (using Ctrl+F or Command+F). Additionally, GA support provides examples of mapping custom dimensions.
Map UA Event to Existing Event with Custom Dimension
Custom Dimensions Scope and Metrics
Both UA and GA4 provide methods to capture additional information during data collection. All custom dimensions in GA4 are either event-scoped or user-scoped.
UA Scope Mapped to GA4
- Event-scoped custom dimensions describe action someone performs and come from event parameters. The value changes as someone performs different actions on your website or app.
- User-scoped custom dimensions describe the person who performs an action and come from user properties. The value changes infrequently as someone uses your website or app.
- A custom metric always has an event scope.
Create Custom Dimensions and Metrics
Before You Start
Before creating custom dimensions, keep the following guidance in mind:
- Always use available dimensions/metrics of GA first, including those recommended but not implemented without user configuration.
- Avoid high-cardinality custom dimensions that clutter reporting with variants. For example, using a custom dimension for unique user ID will create a large number of entries in the “other” row because of the variability of the data element. Instead, use the built-in User-ID feature.
- Verify default features do not address a data need first. Avoid creating a custom dimension for an existing predefined dimension. While unnecessary, the custom dimension will also count against your limit of custom dimensions per property.
- Finally, reference the Google Analytics What’s New page, as new features continue to be added since launch.
Create a Custom Dimension
In this example, a new event, "read_article" needs to capture the author and length of the post a user reads. The example custom dimension and metric is part of the solution.
- From the left menu, click Configure > Custom definitions.
- Click Create custom dimensions.
- Enter a name for the custom dimension (no hyphens, but underscores and spaces are compliant)
- Select a scope for the custom dimension (event-scoped for actions, and user-scoped for user descriptions). Enter a description for the custom dimension.
- Select an event parameter or user property from the list (depending on whether event-scoped or user-scoped) that you’ll collect in the future. Save.
- You will see a value of (not set) for a custom dimension in the first 48 hours.
Custom Dimension UI: Creating an Authorship Custom Dimension
Create a Custom Metric
- From the left menu, click Configure > Custom definitions.
- Click custom metric > Create custom metrics.
- Enter a name for the custom metric (no hyphens, but underscores and spaces are compliant)
- Enter a description for the custom metric.
- Select an event parameter or enter the name of an event parameter that you’ll collect in the future.
- Choose a unit of measurement from the drop-down.
- Save.
Custom Metric UI: Creating an Article Length Custom Metric
As you build up custom dimensions and metrics, you may need to quickly check the number of each within the customizations per property. From Configure, select Custom definitions, then Quota Information.
Custom Dimensions and Metrics Quota