GA4 Custom Dimensions (Definitions & Metrics) Guide

If you search for “GA4” on Twitter, you will quickly learn that a lot of marketers are frustrated and confused by various elements of Google Analytics 4 (and feel as though they need to have an advanced degree in Google Analytics to get basic information that was once readily available in Universal Analytics). Many GA4 users have installed the gtag and created a profile, but haven’t gone so far as to create a new analytics dashboard, dug much more into how GA4 works, or looked at how to get the most out of it.

While custom dimensions have been around for a long time and were a component of Universal Google Analytics, it’s an area where GA4 users have some confusion.

In this post, we’ll walk you through:

  • What custom dimensions are
  • When you’d need to use them (and when you wouldn’t)
  • How to set them up and leverage them in reporting

By the end of the post, you’ll know when and how to use custom dimensions in Google Analytics 4.

What Are Custom Dimensions in GA4?

A custom dimension is a user-created dimension in Google Analytics 4. Dimensions in Google Analytics 4 are attributes or metrics that are associated with your analytic data. 

This means dimensions (and custom dimensions) are additional data to add context (an additional dimension) to your reports. There are a number of dimensions that Google tracks and allows you to layer into reporting by default that – if you’re familiar with either Universal Analytics or GA4 – you’re likely familiar with such as:

  • Campaign or campaign ID
  • Traffic source
  • Google Ads Query
  • Item names for products
  • Geo (city, state, country)
  • Time (day, month, year, hour)

You can see the full list of dimensions available by default in GA4 but hopefully this gives you an idea of the types of things that would qualify as a dimension. 

Custom dimensions are dimensions you create to help you track specific characteristics of either events or users to help aid your reporting. Here are some examples of things you may want to create a custom dimension for:

  • A view of a specific page
  • A click on a specific link (on multiple pages, a specific page, or a collection of pages)
  • A download of a specific file

Again it’s an attribute – an additional data point associated with either a specific event or user – that gives additional context and insight into your reporting. 

Why and When Do You Need Custom Dimensions?

You would want to create a custom dimension if you want to be able to see something specific in reports such as:

  • Users who click on the “request a demo” button from your site’s top navigation (so that you can find out eg which pages this happens most frequently on)
  • Users who visit articles written by a specific author (to see what actions come from that content)
  • Users who viewed a thank you page after completing a form

And you can create custom dimensions around event or user based scopes. This means you can create a custom dimension that applies to an event (a characteristic of an event – such as a specific type of link click) or a user (a characteristic of a user – such as demographic data you’ve collected that’s separate from standard dimensions, eg the user’s profession).

GA4 Custom Dimension Limits (or Quotas)

Google recommends you use the standard dimensions before creating a custom dimension (in other words you don’t need to try to create a custom dimension for something that’s already tracked by GA4, and in fact you may muddy your reporting).

Google also recommends you avoid “high cardinality custom dimensions” which are custom dimensions with over 500 unique values (e.g. an item ID that could be any of over 500 unique item ID numbers).

Keep in mind that you have account limits on the number of custom dimensions you can create, specifically:

ItemStandard property limitsAnalytics 360 property limits
Event-scoped custom dimensions50125
User-scoped custom dimensions25100
All custom metrics50125

GA4 Custom Dimensions Vs. Custom Metrics Vs. Custom Definitions

Google uses these three terms frequently within their interface and documentation, and they can be a bit confusing. Here are the distinctions:

  • Custom Definitions – This is the area within Google Analytics where you can create custom dimensions or metrics.
  • Custom Dimensions – Again these are event or user based attributes that we described above.
  • Custom Metrics – These are metrics that aren’t tracked by default. Rather than an attribute to apply to a metric (e.g. users who viewed X page) custom metrics are metrics in and of themselves (such as phone calls).

How to Create Custom Dimensions in GA4

To create a custom dimension in GA4, you start by navigating to Admin and then selecting Custom Definitions:

A screenshot of how to create custom dimensions in GA4.

One important note here is that you must be an editor or an admin in the analytics property you’re in – if you’re not seeing these options we’re highlighting as we walk through it may be because you don’t have the proper permissions (and/or if you have access to multiple GA properties, make sure you’re in the right one!).

From there, you can create a custom dimension from the Custom dimensions tab:

A screenshot of custom definitions being created in the GA4 interface

Next, you’re going to actually create the dimension by choosing:

  • Dimension Name – Don’t use dashes (underscore or space is fine) and make this something descriptive that you and your team will quickly recognize in reports.
  • Scope – Again this will be event or user based depending on what you want to track.
  • Description – This is just some additional information for anyone looking at this dimension and trying to get a better sense of what is being tracked – be as descriptive, clear, and concise as you can here.
  • Parameter – The parameter for your custom dimension comes from an event parameter. This can be triggered within your website or app, within Google Analytics, or within Google Tag Manager. You need to have an event parameter created that you can reference here before you create a custom definition.
A screenshot of the screen to create a new custom dimension in GA4

Once you’ve completed adding this information, you click save and can see your custom dimension:

A screenshot of adding custom dimensions in your GA4 profile.

If you haven’t created any event parameters for your custom dimension in your GA4 account, we’ll cover that shortly.

How to Edit a Custom Dimension in GA4

If you have your custom dimension set up and want to edit the name or description, you can do that from within the Custom definitions area:

A screenshot of how to edit a custom dimension in GA4

You’re not able to edit the parameter or scope, however, so if you want to make changes to those you’d need to delete the dimension and create a new one.

How to Delete (Archive) a Custom Dimension in GA4

Deleting a custom dimension is a very similar process – you click archive from the same area above, then are prompted to confirm that you want to archive (or delete) the dimension:

A screenshot of how to delete (or archive) a dimension once it's created.

How to Create Event Parameters

If you’re creating a custom dimension but don’t have the event parameter set up to feed the dimension, you can create the parameter a few different ways:

  • Create an event parameter within Google Analytics
  • Create an event parameter on your site (from within the code of the site)
  • Create an event within Google Tag Manager (by creating a trigger and tag)

Once you’ve completed any of these you can then use the event parameter to populate in your custom dimension.

Custom Dimensions & Google Tag Manager (GTM)

If you’ve created a custom event trigger in Google Tag Manager, you need to feed the event parameter into your custom dimension to have the event start to show in certain GA4 views and reports.

Custom Dimensions in GA4 Reporting

You can see your custom dimensions primarily in reporting views that display events, such as: Reporting > Engagement > Events in the left navigation within GA4.

Create Your Own Google Analytics Dashboards

If you’re struggling with certain aspects of GA4 and find looker studio too complicated, you may want to use a third-party dashboard to help you monitor key metrics.

For WordPress users, the ShareThis Google Analytics Dashboard for WordPress can help you monitor your traffic and engagement for free with just a few clicks.

About ShareThis

ShareThis has unlocked the power of global digital behavior by synthesizing social share, interest, and intent data since 2007. Powered by consumer behavior on over three million global domains, ShareThis observes real-time actions from real people on real digital destinations.

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