Custom Dimensions in Google Analytics 4 (GA4)

Custom dimensions are a powerful feature in Google Analytics 4 (GA4) that allow users to measure and analyze data that is not captured by default dimensions. They are user-defined dimensions that can be tailored to measure unique characteristics of a user or event that are specific to your business needs. For instance, you might create a custom dimension to store client IDs.

What are Custom Dimensions in GA4?

In the context of GA4, a custom dimension is an event parameter. This parameter can be an automatically collected parameter, custom parameter, or user property. However, it's important to note that sending personally identifiable information (like name, email address, house address, phone number, social security number, etc.) to your GA4 reporting view as a value of the custom dimension is against the Google Analytics terms of service.

There are two main types of custom dimensions in GA4:

1. Event-scoped custom dimensions: These are custom dimensions whose value is calculated and sent for each event. They are created by registering a parameter with event scope in the GA4 user interface.
2. User-scoped custom dimensions (user properties): These are custom dimensions whose value is calculated and sent once for each user. They are created by registering a parameter with user scope in the GA4 user interface.

Advantages of Using Custom Dimensions in GA4

The use of custom dimensions in GA4 offers two main advantages:

1. In your event report, you see a new data card added for every logged event parameter you registered as a custom dimension. This enriches your existing event reports.
2. You can report on the same event parameter for as many events as you like without passing the same parameter repeatedly for each event.

Differences Between Custom Dimensions in Universal Analytics and GA4

Custom dimensions in Universal Analytics and GA4 differ in several ways:

1. Different scopes: In Universal Analytics, a custom dimension can have hit, session, user, or product scope. In GA4, a custom dimension can have either event or user scope.
2. Different processes for creating custom dimensions: In Universal Analytics, creating a custom dimension involves configuring the custom dimension in the user interface and writing a code to send the values of the custom dimension to the reporting view. In GA4, it involves sending an event parameter along with an event and registering the logged event parameter as a custom dimension in the user interface.
3. Different quotas for custom dimensions: In Universal Analytics, you can create up to 20 custom dimensions per property (or up to 200 for GA 360 users). In GA4, you can create up to 50 event-scoped custom dimensions and 25 user-scoped dimensions per GA4 property.

Creating Custom Dimensions in GA4

Creating custom dimensions in GA4 is a straightforward process. Here's a step-by-step guide on how to do it:

Step 1: Start by logging into your Google Analytics account. Click on 'Admin' at the bottom left corner of the page.

Step 2: Ensure you are in the correct account and property. In the 'Property' column, click on 'Custom definitions'.

Step 3: In the 'Custom dimensions' tab, click on 'Create custom dimensions'.

Step 4: Fill in the Details: You will be prompted to complete the following information:

1. Dimension Name: Enter a unique name for the dimension. Note that you can't use hyphens in the name, but you can use underscores and spaces instead.
2. Scope: Choose a scope for the custom dimension. The scope can be 'Event', 'User', or 'Item'. An 'Event' scope provides information about an action that a user performs. A 'User' scope provides information about the user who performed the action. An 'Item' scope provides information about the products or services that users interact with in an event.
3. Description: Enter a memorable description for the custom dimension.
4. Event Parameter/User Property: Choose the source of data. This could be an item parameter (for Item scope), an event parameter (for Event scope), or a user property (for User scope).
5. Save the Custom Dimension: Click 'Save' to create the custom dimension. You will see a value of '(not set)' for a custom dimension in the first 48 hours.

Remember, you must have the Editor or Administrator role to create custom dimensions. Also, be mindful of the quotas for custom dimensions. For standard GA4 properties, you can create up to 50 event-scoped custom dimensions and 25 user-scoped dimensions.

Best Practices for Custom Dimensions in GA4

When using custom dimensions in GA4, it's important to follow best practices to ensure you're getting the most out of your data analysis. Here are some key points to consider:

1. Use Default Dimensions and Metrics First: Before creating custom dimensions and metrics, make use of the default dimensions and metrics provided by GA4. These default dimensions and metrics are designed to cover a wide range of common data analysis needs and can often provide the insights you're looking for without the need for customization.
2. Avoid Unnecessary High-Cardinality Custom Dimensions: If you have a standard GA4 property, avoid creating unnecessary high-cardinality custom dimensions. High-cardinality dimensions have a large number of unique values and can negatively impact your reports, causing data to aggregate under the '(other)' row. Examples of high-cardinality dimensions that should be avoided include using a custom dimension for a unique ID per user (use the User-ID feature instead), using a custom dimension to send unique IDs per session (like a Session ID), and sending a timestamp as a custom dimension.
3. Don't Duplicate Predefined Dimensions: Registering a custom dimension for a parameter that is already a predefined dimension, such as the page and screen dimensions, or transaction ID, is not a best practice. It will not affect cardinality, but it will use one of your custom dimension quota.

Managing Custom Dimensions in GA4

In GA4, you can edit, view quota information for, and delete custom dimensions. To edit or delete a custom dimension, navigate to your GA4 property view, click on the 'Configure' link, then 'Custom Definitions', and select the relevant options for the custom dimension you want to manage. Note that deleting (archiving) a custom dimension is permanent and cannot be undone.

In conclusion, custom dimensions in GA4 are a versatile tool that can greatly enhance your data analysis capabilities. By understanding and effectively using custom dimensions, you can gain deeper insights into your users' behavior and optimize your marketing strategies accordingly.

Finally, if you'd like to know more about custom metrics, please check this full guide: Custom Metrics in GA4