Definition:
A custom dimension is a descriptive attribute configured in an analytics tool to analyse information beyond that provided by its predefined dimensions. It allows data to be classified according to characteristics relevant to the website, application or business.
Unlike predefined dimensions, it requires the collection of the corresponding information to be configured. Creating the dimension does not make the tool collect that data automatically.
Custom dimension in Google Analytics
In Google Analytics 4, custom dimensions allow information sent through user properties or event and item parameters to be analysed. Their scope determines what each piece of data refers to:
- User: a characteristic of the user.
- Event: a detail of a recorded action.
- Item: a characteristic of a product or service included in an ecommerce event.
To use this data in reports, its transmission must first be configured and the dimension must then be registered in the property’s custom definitions. The information is usually available for reporting between 24 and 48 hours after the setup is completed.
GA4 sets limits for custom dimensions. Standard properties allow 25 user-scoped, 50 event-scoped and 10 item-scoped dimensions to be registered. For Analytics 360 properties, the limits are 100, 125 and 25, respectively.
It is useful to use predefined dimensions when they already cover the information needed, avoiding duplication and consuming quota without adding a new classification.
Examples of custom dimensions
The following examples show what information a custom dimension can collect and what analysis it makes possible:
- Account type in an application: a user-scoped dimension can collect values such as "free" or "premium". It allows the use of particular features to be compared between the two groups.
- Type of form submitted: an event-scoped dimension can collect values such as "contact", "quote" or "demo". If the forms share the same submission event, this data makes it possible to distinguish which requests are received.
- Product material: an item-scoped dimension can collect values such as "cotton", "wool" or "polyester". In ecommerce events, it allows units sold or revenue to be analysed by material.
- Customer category from the CRM: a user-scoped dimension can collect values such as "individual" or "business". It allows the behaviour of these groups to be compared in aggregate, provided that the integration sends this category to GA4.
The categories used must not contain names, email addresses or other data that Google could recognise as personally identifiable information.
Objectives
Custom dimensions allow analysis to be tailored to business questions, patterns of behaviour to be identified and recorded interactions to be related to information specific to the organisation.
They can be used as analysis criteria or breakdowns in reports and explorations, as well as in compatible filters, comparisons and segments. Their availability depends on the scope and the dimensions and metrics selected.
A dimension describes a characteristic; a metric quantifies a value. In the forms example, the form type is the dimension, "contact" and "quote" are its possible values, and the number of submissions is the metric. This combination shows both which requests are received and how many fall into each category.