Once you set up cross-domain tracking in Google Analytics 4, it allows you to see sessions from two related sites (such as an e-commerce site and a separate shopping cart site) as a single session rather than two separate sessions.
Google Analytics uses 1st-party cookies to set an identifier for each unique user and session to a website.
Without cross-domain measurement , new cookies with new identifiers are set for each domain a user visits. Analytics count these new cookies with new identifiers as separate users with separate sessions.
With cross-domain measurement , the same identifiers are passed from one site to another via a URL parameter identified by the key '_gl:', for example: 'https://www.mysite.com/?_gl=1*abcde5*.'
How to Set up Cross-Domain Tracking in GA4?
For your Universal Analytics property, you used to configure cross-domain measurement via code (either in source code via analytics.js or gtag.js or via Google Tag Manager). For your Google Analytics 4 property, however, you can do this via the Admin page.
Follow the steps below to set up your cross-domain tracking:
Select Admin from the menu on the left.
Find Data Streams under Property.
Click Web and then choose a web data stream
In the web stream details, click Configure tag settings:
In the Settings section, click Configure your domains
Under 'Include domains that match ANY of the following conditions': - Choose a match type. - Under Domain, add the identifier for the domain you want to match (e.g., example.com). - Click Add condition to add the next domain. (Add each domain you want to include in cross-domain measurement.) Conditions are evaluated using the OR method.
Click Save to finalize the process.
Now that you have completed all the steps above;
Open a page of your site that contains a link or a form that points to a domain you configured for cross-domain measurement.
Then, click the link or submit the form to navigate to the destination domain.
Verify that the URL in the destination domain contains the linker parameter '_gl'; for example: - https://www.mysite.com/?_gl=1*abcde5*.
