The Ultimate Guide to GA4 Cross-Domain Tracking

The Ultimate Guide to GA4 Cross-Domain Tracking

If your business has several websites contributing to the same user journey, you probably know how important Google Analytics is for understanding what users do and improving your online strategy. It can get tricky when you need to cover multiple domains. 


Luckily, Google Analytics 4 (GA4) has a solution called cross-domain tracking, which helps you see how users engage with your websites, even if they’re on different domains. In this comprehensive guide, we’ll explain cross-domain tracking in GA4 more straightforwardly and give practical advice to help you use this powerful feature effectively. 


So, if you manage multiple websites, keep reading to make sense of the data and improve your understanding of user interactions.

Let’s dive right in!

Understanding Cross-Domain Tracking in GA4

Let’s break down cross-domain tracking in simple terms.


Say that your business owns two websites that have different domains. Now, let’s say you have a visitor who landed on the first website, and GA4 automatically stored a cookie on that visitor’s browser. Somewhere on that website, there is a link the visitor clicked, and he was redirected to your second website. This second website is part of the same user journey.


GA4 is also activated on this website, but since this is a different domain, the cookie value is also different. GA4 on this domain cannot access the cookie stored on the first domain. So, even though the user is the same, Google Analytics treats these actions as separate users. Instead of one user, your reports will now show two users.


But cross-domain tracking takes care of this. Here’s how it solves the problem: A visitor lands on the first website, and a cookie gets stored. Then, when he gets redirected to the second website, the URL will automatically contain cookie information. GA4 will take that information from the URL and update the cookie on the second website. So, the same visitor will have the same cookie value on both websites.


In technical terms, Google Analytics gives each user and their session a unique identifier. The user gets a client ID, and the session gets a session ID. Doing this ensures that the information in your reports is more precise.

The Significance of Cross-Domain Tracking

To put it in even more concrete terms, let’s consider a common scenario:


Imagine you’re running a marketing campaign that directs users to discover your product or service on website A. Those interested are then sent to website B to complete an action, such as purchasing or signing up.


 If you haven’t set up cross-domain tracking:


You won’t be able to properly analyze your marketing performance since you can’t pinpoint which campaigns drive sales or conversions. Your GA4 reports will appear inflated, showing more users and sessions than there are. This occurs because each visit from the first website to the second is counted as a new user with a new session.

Now that we established the significance of cross-domain tracking, let’s learn how to put it into action!

call to action button

Requirements for Setting Up Cross-Domain Tracking

To set up cross-domain tracking, there are a few essential steps you need to take care of:

  • All your websites must be on the same GA4 property.
  • You must configure cross-domain tracking in the GA4 interface.

How To Set Up Cross-Domain Tracking in GA4?

  1. Go to Admin > Data Streams > Choose your website’s data stream > click on “Configure tag settings.”

Data streams screenshot

Configure settings screenshot

  1. Under “Configure tag settings,” click “Configure your domains.”Configure domains screenshot
  1. Set the first condition for your first website and the second for your second website. If you want to, you can write even more complex conditions by using Regular Expressions.
  2. Click “Save”.

 After saving your settings, you can test the setup.

screenshot of cross domain linking configuration

Testing the Setup

You can check your cross-domain configuration by clicking the link on the first website (which will take you to the second page). The _gl= parameter should be included in the URL of the second website. You can also see if the _ga cookie is the same. Run this test on both domains. The value of the _ga cookie must be the same on both domains.

Referral Exclusions

Self-referral occurs when traffic is directed to you from your domain. Analytics should detect self-referral and remove it from the list of referring domains by default. It is essential to note you don’t have to manually configure a referral exclusions list to do cross-domain tracking. GA4 will handle this automatically once you’ve configured your domains.


However, it’s advisable to include any third-party domains that play a role in transactions or other interactions in your referral exclusion list. Typical examples are payment gateways like PayPal or email marketing platforms that send password recovery emails to your subscribers.


In rare instances, your domain might show up in the referral report. If this occurs, you should add it to the referral exclusion list. Additionally, you can create a source/medium report within GA4 to analyze which channels are being categorized as referral traffic.

What About Subdomain Tracking?

Subdomains help you divide and manage different parts of your website, like blogs, online stores, or localized content, while keeping them connected to your leading site.


If your business operates on multiple websites, but they are using the subdomains of the same domain, you don’t need cross-domain tracking. GA4 handles this automatically. Cross-domain tracking involves only completely different domains.


So, there’s no need to set up anything specific for tracking subdomains. Avoid adding your subdomain or domain in the “Configure your domains” section.



To sum everything up, here’s a short overview of the points we covered in the article!

What Is Google Analytics 4 Cross-Domain Tracking?

It’s a technique that lets webmasters, marketers, and analysts transfer user identifiers from one domain (A) to another (B) while preserving session data. This allows tracking the same visitor across different websites.

Why Is Cross-Domain Tracking Important?

Without it, visitor counts become less accurate, and additional sessions are created when users move to another domain, making it seem like different users.

Do I Need to Set Up Tracking for Subdomains?

No, cross-domain tracking is not required for subdomains of the same parent domain. Google Analytics 4 can naturally track visitors across subdomains without any extra setup.

Do I Need to Set up a Referral Exclusion List?

No, GA4 does this automatically according to the list of domains you specify. A referral exclusion list is typically used for specific domains like payment gateways.

How Can I Test Cross-Domain Tracking?

You can validate your cross-domain setup by clicking a link on the first website, which should redirect you to the second website. Check if the URL of the second website contains the “_gl=” parameter. Additionally, ensure that the “_ga” cookie has the same value on both domains. Pay attention to the “Domain” column in the cookie list.

Ready to Supercharge Your Insights with GA4?

If you’re looking to unlock the full potential of Google Analytics 4 and need expert guidance, don’t hesitate to get in touch with our team at Play Media! We specialize in GA4 and are here to help you make the most out of this powerful tool. Contact us today, and together, we’ll elevate your data-driven journey, ensuring you’re on the path to success.


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