Create Custom Dimensions in GA4 | Use Case + FAQs

Google Analytics 4 will replace Universal Analytics on July 1st, 2023. GA4 has many new features and improvements, and one of the biggest is that it lets you add more custom dimensions.

In this blog, we will go over:

Here is how to track and analyze data beyond the standard metrics provided by GA4.

What Is a Custom Dimension?

In Google Analytics 4 (GA4), custom dimensions are additional information used to enrich the data collected from your website or app.

Along with a custom metric, a custom dimension falls under the Custom Definitions segment of GA4. Custom dimensions and metrics are set at the property level in an Analytics account.

Dimensions’ common aim is to support strategies based on GA data – they offer insight into website traffic and user behavior, let you identify trends and patterns in your data, and make informed decisions about optimizing and improving the site or app.

The new version of the GA platform lets you create a custom dimension for custom reports that provide insight into user behaviors or activities that go beyond tradition.

Default Dimensions in GA Interface

There are many predefined dimensions in Google Analytics 4, like Transaction ID, User ID, product name, etc. They help us connect the dots between the user, website, product, event, or other.

Here are some examples of default dimensions for the purchase of an eCommerce object; for example, Nike sneakers:

  • Item brand: Nike
  • Item variant: 41, Green
  • Item ID: 345657678
  • Coupon code: XMAS2022
  • Currency: USD

Built-in dimensions are listed in the Google Analytics support blog post. If you need a dimension not listed here or in GA4 Dimensions & Metrics Explorer, you should create a new, custom one using event parameters.

Why Add Custom Dimensions?

Custom dimensions are compelling due to the flexibility they offer.

A custom dimension collects non-standard event parameters and allows you to use new data in the platform. Adding a new event parameter in any event, you’re sending to GA4 (regardless of if it’s coming from GTM or another way) allows users to configure custom dimensions.

Custom dimensions supplement tracking of specific events or actions important to a business. Google Analytics events enriched/supplemented with a custom dimension make deep audience segmentation possible, so you can cross-examine and analyze data to make better business decisions.

Also, using custom dimensions may help you map user journeys across devices and optimize experiences for target audiences.

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Custom Dimensions in Universal Analytics vs. GA4

Custom dimensions are different in GA4 than in Universal Analytics, mostly due to scopes. Scope refers to the level at which we apply a particular piece of data.

There are multiple scopes used for custom dimensions in Google Analytics 3 (UA):

  • event scoped custom dimensions
  • user scoped custom dimension
  • product scoped custom dimensions
  • session scoped dimensions

In GA4, a custom dimension has either an event or a user scope. It has grown to 25 user scoped custom dimensions and 50 event-scoped dimensions versus just 20 sessions, product, event, and user scoped custom dimensions in Universal Analytics.

Custom dimensionsUniversal Analytics (GA3)Google Analytics 4 (GA4)
Types of scopesEvent
Number of custom dimensions
(per property)
2025 user-scoped
50 event-scoped

There are some loopholes for creating custom dimensions with user or product scope in Google Analytics 4:

• If you want to create a custom dimension with the user scope, create User properties in GA4.

• If you want to create a custom dimension with the product scope in GA4, use item parameters like item_category, item_category_2, item_category_3, and so on.

Create Custom Dimensions in GA4 with GTM

Here is a mini case study of new custom dimensions added to a client’s Google Analytics property to better understand user decisions.

Collecting More Than Generic Data

Our client is in recruiting business, with thousands of jobs available every day. Their website funnel looks like this: 

  1. Candidate creates a profile with occupation, preferred positions, and other information.
  2. Then they can view a list of jobs presented to them.
  3. Once they’ve chosen the job, they accept it, and that’s where their journey exits the website. 
  4. A recruiter does one more phone contact to validate the job application and verify the details and start date.
  5. The CRM is updated when the candidate starts working.

The last two steps are considered offline events since they don’t occur on the client-side website. We got a hunch about a lot of custom information to define and track in GA4.

Event Parameter Workaround for New Custom Dimension

Before GA4 implementation, the only place where data is collected is CRM. The clients have a custom CRM unsuitable for data collection and need an appropriate structure for marketing attribution. It behooves them to implement GA4, which will give them insight into how jobs perform and which channel brings the most registrations, applications, and recruitments.  

Let’s say we’ve created a funnel and decided to track necessary user steps. Those would be:  

  • Register 
  • View Job offer
  • Accept Job offer
  • Change Status to Working

We named them accordingly in GA4: 





Since the first three actions are happening on the website, and their website is custom-made, we asked their developers to execute a dataLayer push for the events. 

The status change event is happening on the back end, so we needed a different approach. 

That’s where GA4 measurement protocol hits the spotlight. This mechanism allows us to send real-time (or pseudo-real-time) events that are not standard user interaction on the website and connect online and offline behavior. For that, we needed a couple of pieces of information to collect, like the Google Analytics client ID and the user ID generated by the website. That way, we tie the “offline” event sent via the GA4 measurement protocol to the candidate for performing the action. 

Setup: Custom Dimensions in GA4

Now, the setup is quite simple. We used a custom event pushed to dataLayer as a Google Tag Manager trigger and sent the event to Google Analytics 4.

The simple version of a tag looked like this:

Once the events are tracked, simple use of GA4 exploration reports looks like this:

Simple exploration report with newly tracked events, crossed with a standard dimension – default channel grouping

Going a Step Further with Custom Dimensions

This setup is proper and can be crossed with the most vital dimensions. But we wanted to move up and see which jobs have the highest view rate, acceptance rate, and hiring rate, as well as get insight into step-by-step conversion rates.

This was a perfect opportunity to use custom dimensions and metrics and tailor the Google Analytics 4 setup to our needs.

So, together with the client’s stakeholders and marketing managers, we used event parameters to supplement events with job information and connect them with other data sources:

  1. job ID (the most important parameter); the joining key with other sources – a unique identifier of a specific job offer.
  2. sector (i.e., logistics)
  3. profession (more detailed, i.e., storage manager)
  4. salary range
  5. salary type, etc.

Each of those custom dimensions represents one parameter which should be paired with every job-related event and sent to Google Analytics.

We asked developers to send a detailed data Layer push event. This is what the instructions looked like for one of the events:

With an example provided:

After testing and confirming that all custom parameters work correctly, the next step was registering custom dimensions!

After proper custom dimensions, we finally created some reports. We used Exploration reports to set up a job funnel segmented by our newly created dimensions. One of the custom reports looks like this:

Exploration report with newly created custom dimensions

This event report provides excellent insight into the popularity of sectors, professions, and conversion rates between each step. When crossed with source/medium or Geo-Location dimensions, it also provided a lot more information about the traffic sources & the location of their candidates. 

However, the most significant value of this setup is providing a way to combine any data that has information about jobs with these reports by exporting data from all sources and combining it in Google Sheets, BigQuery, Google Data Studio (Looker Studio), or elsewhere. 

So, now you can have data from multiple sources, with different purposes and various information, all combined in one place and ready to explore, extract, analyze and deliver powerful insights. 

Overall, custom dimensions are a powerful asset in GA4 that may assist you in gaining a deeper insight of your website’s traffic and user behavior, as well as making more educated decisions about how to build your business.


Where are custom dimensions in GA4?

Find custom dimensions in Google Analytics 4 Custom definitions section of the GA4 property settings. Here, you can create and manage custom dimensions. You have to be logged in to your Google Analytics account and navigate to the property you want to work with.

From the left-hand menu, click on Custom definitions  under the Property section. This will open a list of all the Custom dimensions and metrics  associated with your property.

Custom dimensions can be used in which reports?

Custom dimensions can be used in standard and custom reports, as a primary dimension in custom reports, and secondary in standard ones. 

How many custom dimensions are allowed in GA4?

A custom dimension in Google Analytics 4 has either an event scope or a user scope. There are 25 user scoped custom dimensions and 50 event scoped dimensions in GA4.

Compared to Universal Analytics’ 20 session scoped custom dimension, product, event custom dimension, and user scoped custom dimension, GA4 offers much more flexibility.

What are custom metrics in GA4?

A custom metric in Google Analytics 4 lets you measure an action on a website that isn’t in the built-in metrics list in GA4.

A custom metric quantifies a measurable action: how much or how often an action is made on the website.

A custom dimension qualifies what the action is and how action happens on the website.

What scope applies to custom metrics?

Custom metrics in Google Analytics 4 have just one scope: the event scope.

You can create an event-scoped custom metric by inserting a parameter with event scope in the GA4 user interface.

Custom metric values in GA4 are provided through recorded event parameters.

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