Table of contents for how to check cross-domain tracking in Google Analytics:

1. Introduction to cross-domain tracking
2. Troubleshooting steps for cross-domain tracking
3. Check if both domains are validated under the same property
4. Validate source domain in the referral exclusion list in Google Analytics
5. Check if the allow linker in GTM is set to true
6. Target domain should have a linker parameter in the URL

Introduction to cross-domain tracking

Cross-domain tracking allows you to uniquely identify users across different domains. Okay, let’s make it more simple.

Let us take an example to understand in detail. Whenever a user lands on website A,  a _ga cookie with a random identifier is dropped in the visitor’s browser. When a user navigates between the pages on the same domain, GA identifies that you are the same person since the cookie value is the same.

Now, let’s say you have navigated to website B from website A, a cookie value from domain A will not reach website B and a new cookie will be created. So, the result would be, two separate visitors, one on website A and one on website B. 

But in some scenarios you would like to have the same cookie value when the user navigates between domains to understand the measurement.

In this article, we would be mainly looking into troubleshooting techniques to check if the cross-domain tracking in Google Analytics.

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Steps to check cross-domain tracking in Google Analytics

If cross-domain tracking is working fine, the traffic from one domain to another domain should be attributed to the same source and medium. 

To troubleshoot we have to make sure that the four requirements below are met:

1. Check if both domains are validated under the same property.
2. Validate source domain in the referral exclusion list in Google Analytics
3. Check if the allow linker in GTM is set to true
4. Target domain should have a linker parameter in the URL.

These are four main checks to validate your cross-domain tracking. These checks are described in more detail below.

Check if both domains are tracked under the same property

The main requirement is to have the same Google Analytics property on both the source domain and destination domain. Cross-domain tracking only works if both the domains are tracked under the same property. 

Let’s see where to check the property ID and how to validate if both the domains have the same tracking ID. 

To check this, follow the below steps:

Step-1: Log in to your Google Analytics account.

Step-2: Click on the ‘Admin’ section in the left-hand corner of the console.

Step-3: Under ‘Property’, click on the tracking info. A screen with account, property, and view would appear. Click on ‘Tracking info’.

Step-4: Click on ‘Tracking code’, below ‘Tracking info’.

Step-5: By selecting ‘Tracking code’, you will see the tracking ID in the console.

Note: This ID should be implemented on both the source and destination domain.

Step-6: Add the Google Tag Assistant Chrome extension to your browser from the Chrome web store and pin the extension.

Step-7: Open your source domain and click on the Tag Assistant extension and check the property ID.

Step-8: Follow the same steps for the destination domain and check if the property ID is the same.

Step-9: You can also validate the same using the developer tools. Open the developer console on the website by using the command ctrl+shift+I. In the network console, filter for collect in the header you would see the property ID shown as below.

Step-10: Repeat the same steps on the destination domain and validate if the property ID is the same.

Validate source domain in the referral exclusion list in Google Analytics

Validate if the source domain should be included in the referral exclusion list in Google analytics settings so that Google considers it as direct traffic. 

If your source domain is not added to the referral exclusion then Google records this traffic as having originated from source/referral.

Follow the below steps to add the site to the referral exclusion list:

Step-1: Log in to your Google Analytics property.

Step-2: Click on the ‘Admin’ section in the left-hand corner of the console.

Step-3: Under ‘Property’, click on ‘Tracking info’. A screen with account, property, and view will appear. Click on ‘Tracking info’.

Step-4: Under ‘Tracking info’, click on the ‘Referral exclusion list’.

Step-5: A screen like below will appear. Click on the ‘Add referral exclusion’ button.

Step-6:  Enter your source domain name, in the referral exclusion list.

Step-7: Click on ‘Create’ after entering the source domain name in the referral exclusion list.

Target domains trackers have the allow linker set to true

Step-8: check if the source domain is included in this section.

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Check if the allow linker in GTM is set to true

Step-1: Log in to your Google Tag Manager account.

Step-2: Click on the ‘Variables’ tab on the left-hand side of the console.

Step-3: Scroll down to the user-defined variables and select the ‘GA Tracking code’ variable.

Step-4: Click on the pencil icon on the right side of the variable configuration and open ‘More settings’.

Step-5: Select ‘Cross-domain tracking’ from the options.

Step-6: Check if the website URLs are updated in the ‘Auto-link domains’ section under ‘Cross-domain tracking’.

Step-7: Additionally, also validate if the ‘allowLinker’ value is set to ‘true’ in the ‘Fields to set’ section.

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Check if the target domain has the linker parameter in the URL

The link directed from the source domain to the destination domain should have the linker parameter. Let us take an example to understand this better. 

The user lands on domain A and client ID (1234567.69798700) is created, when the user clicks on a link on domain A that redirects to domain B.

So, when the user redirects from domain A to domain B, it should have a query parameter in the URL which will look something like below:

www.optimizesmart.com?_ga=23457586.689798080

The query parameter in the URL should have the ga client ID which is then passed to domain B. Our main goal here is to validate the same value of ga cookie across the source and destination domains.

To validate if this value is passed on the destination domain, follow the below steps:

Step-1:  Open the source domain in the browser.

Step-2: Using the command Ctrl+shft+I open the developer console and filter for collect in the network tab.

Step-3: In the header, scroll down and check for cid value and make a note of it.

Step-4: Follow the same steps in the destination domain, check for the client ID, and match it with the one you have noted. Ideally, these two cid’s should be the same.

Once all four of these checklists are passed, cross-domain tracking should work without a hitch.

Other articles on cross-domain tracking

• Cross Domain Tracking in Google Analytics – Complete Guide
• Google Analytics Subdomain Tracking Tutorial
• Cross Domain Tracking with Google Tag Manager (GTM)
• Cross Domain Tracking in GA4 (Google Analytics 4) Setup Guide
• Setting up Sales Funnel across websites in Google Analytics
• Google Analytics cookies: _ga cookie, _utmb, _gat – Tutorial