The implementation method is completely new when it comes to updating your existing analytics property (Universal Analytics) to GA4 or setting up a new analytics property in GA4.
In this article, I am going to talk about how to set up cross-domain tracking in Google Analytics 4.
Cross-domain tracking
Cross-domain measurement allows you to uniquely identify your website user across different domains.
With cross-domain tracking, activity is attributed to the same user regardless of domain. This helps to keep user counts more accurate and gives you a complete view of a user’s journey across domains.
When you set up cross-domain tracking, and when an outbound link leads to another domain, the enhanced measurement option to track outbound links is ignored. This allows the same user to be tracked across different domains.
Cookies and cross-domain measurement
Google Analytics uses first-party cookies to identify unique users on the website.
If you have multiple website domains with analytics tracking implemented, GA will create a new cookie every time a user navigates through the website domains.
In this case, the same user will have a separate cookie for each domain and be counted as a separate user for each domain.
With cross-domain tracking implemented, when the user navigates to a different domain, analytics cookies are passed from one domain to another using the URL parameter identified as key ‘_gl’.
For example, https://optimizesmart.com/?_gl=1*abcde5*
This way, you can identify the same user across your domains and get a complete view of the user’s journey.
In the legacy version of Google Analytics, a complicated setup was required to set up cross-domain tracking.
It was usually done by using the ‘allowlinker’ parameter hardcoded into every single Google Tag Manager tag (if you are using Google Tag Manager) or in every ‘gtag.js’ (Global Site Tag) call.
In the case of Google Analytics 4, setting up cross-domain tracking has been made very simple, and no hardcoded tagging is required like in the earlier version.
It can now be achieved with only configuration settings in the ‘Admin’ section.
Follow the simple steps below to get started:
Note: You will need edit-level access to the GA4 property to set up cross-domain tracking.
Example reference: In the below steps, we are setting up cross-domain tracking between two different GA4 properties.
Sample website domain: example.com
Sample website 2 domain: example2.com
Step 1: Navigate to your GA4 Property. Click on the ‘Admin’ link available on the left-hand side.
Step 2: A new overlay will appear as below. Click on ‘Data Streams’.
Step 3: Data streams show you all the available streams (GA4 properties and their details).
Select the web property for which you want to set up cross-domain tracking. In our case, we will select ‘Sample Website’ with the domain ‘example.com’.
Step 4: An overlay will appear like the one below. Click on the ‘Tagging Settings’ options under additional settings.
Step 5: A new overlay will appear below, with various features available. As of now, we are focusing on cross-domain tracking, so click on the ‘Configure Your Domains’ option.
Step 6: You will see the configuration panel opens up like below.
You will see a really important note at the top.
If you are using a legacy version of Google Analytics universal properties and want to set up cross-domain tracking between GA4 and a legacy version, then you need to map the settings between each type of property.
You can click ‘Learn more,’ which will guide you through the required settings.
In our case, we are setting up cross-domain tracking for GA4 properties, and it will be simpler.
Here we just need to add our domains, and, as I said earlier, no hardcoded changes are required.
Just click on ‘Add condition’.
Step 7: You will get the option to select the math type for the domain conditions. You can use any of the following to meet your business needs.
Contains: Includes part of a string in the domain name.
Begins With: Includes domains that start with a specified string.
Ends With: Includes domains that end with a specified string.
Exactly Matches: Exactly matches the whole part of a domain string.
Matches Regex: Powerful lookups to match multiple domains from the list specified.
In our case, we will use a simple match type – ‘contains’.
Step 8: Add the domain like the one below. We are adding the domain name for the sample website 2.
(Match Type: Contains and Domain: example2.com)
Now click on ‘Save’.
Step 9: Now navigate to the data streams tab in the ‘Admin’ section and select another web property. In our case, we will select the domain for sample website 2 – example2.com.
Step 10: An overlay will appear like the one below. Click on the ‘Tagging Settings’ option under additional settings.
Step 11: Click on the ‘Configure your domains’ option.
Step 12: You will see the configuration panel open up like below. Just click on ‘Add condition’.
Step 13: You will get the option to select the math type for the domain conditions.
In our case, we will use a simple match type – ‘contains’.
Now add the respective domain of the first website in the textbox next to the match type.
Match Type = Contains and Domain = example.com.
Step 14: Click on ‘Save’.
Congratulations!!! You have successfully configured the cross-domain tracking.
Now the cross-domain setting is done, when the users navigate from one website to another, it will be counted as a single visit, and all the traffic sources will be consistent throughout.
You can debug the cross-domain tracking functionality in order to validate the setup.
Navigate to any of your websites and click on the link to another domain for which you have configured the cross-domain tracking.
Once you click the link, you will be redirected to the new domain, and you can check the URL will be populated with a new ‘_gl’ parameter like the one below.
If you see the ‘_gl’ parameter in the URL, your cross-domain tracking is working properly.
This ‘_gl’ parameter will continue the session from the previous domain to the new domain, and it won’t be treated as a new user.
It will also pass all the GA information it has on the earlier domain, such as traffic source, attribution modelling, and GA cookie values.
What will happen if you set up individual data streams for each subdomain in a single GA4 property?
Will it result in inflated website traffic?
GA4 automatically tracks traffic from all subdomains within a single property by default.
But you can also set up individual data streams for each subdomain.
When you set up individual data streams, GA4 tracks the data for each subdomain separately.
This can be useful if you want to see data specifically for each subdomain rather than combined data for all subdomains.
It will not result in inflated website traffic as GA4 uses a unique measurement ID for each data stream, so it will not double-count the traffic.
Each data stream will have its own metrics and reports, allowing you to analyze the data separately.
However, there are some major downsides to setting up individual data streams for each subdomain in GA4:
1)Setting up individual data streams for each subdomain requires more tracking setup, maintenance and troubleshooting. Hence increased complexity and higher data management costs.
2) With individual data streams for each subdomain, it can be harder to see the overall picture of the website’s performance across all subdomains as the data is split across multiple data streams. This can make it more difficult to identify trends and patterns in the data.
3) When you set up individual data streams for each subdomain, tracking cross-domain behaviour, such as a user’s journey across different subdomains, can become harder.
4) Individual data streams for each subdomain can lead to a lack of data continuity, making it harder to compare data over time.
5) Individual data streams for each subdomain can make creating and managing audiences, custom dimensions and metrics, and other reporting features more difficult.
6) If different teams are responsible for different subdomains, each team may have their own methods and processes for setting up and configuring data streams, tracking events, and analyzing data which can make it difficult to compare data from different data streams.
The inconsistencies in how data is collected and analyzed across subdomains can also make it difficult to identify trends and patterns in user behaviour across subdomains.
Frequently Asked Questions About GA4 Cross-Domain Tracking
What is cross-domain tracking?
Cross-domain measurement allows you to uniquely identify your website user across different domains. With cross-domain tracking, activity is attributed to the same user regardless of domain. This helps to keep user counts more accurate and give you a complete view of a user’s journey across domains.
How does cross-domain tracking work?
Google Analytics uses first-party cookies to identify unique users on the website. With cross-domain tracking implemented, when the user navigates to a different domain, analytics cookies are passed from one domain to another using the URL parameter identified as key ‘_gl’. For example, https://optimizesmart.com/?_gl=1*abcde5* This way you can identify the same user across your domains and get a complete view of the user’s journey.
Is it easier to set up cross-domain tracking in GA4?
In the legacy version of Google Analytics, a complicated setup was required to set up the cross-domain tracking. In the case of Google Analytics 4 setting up cross-domain tracking has been made very simple and no hardcoded tagging is required like in the earlier version. It can now be achieved with only configuration settings in the ‘Admin’ section.
How do I know if cross-domain tracking is working correctly?
You can debug the cross-domain tracking functionality in order to validate the setup. Navigate to any of your websites and click on the link to another domain for which you have configured the cross-domain tracking. Once you click the link you will be redirected to the new domain and you can check the URL will be populated with the new ‘_gl’ parameter like below. If you see the ‘_gl’ parameter in the URL that means your cross-domain tracking is working properly.
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