GA4 - Cross-Domain Tracking
Table of contents
In short
Many companies have several websites that they want to track across domains. For example, products are advertised on a separate website, while the checkout takes place on another website.
Cross-domain tracking measures user sessions across multiple domains and provides a complete picture of the user journey. It is particularly indispensable for such scenarios, but often poses challenges.
This guide shows how cross-domain tracking can be set up easily and effectively in GA4.
What is cross-domain tracking?
Cross-domain tracking, combines user sessions across different domains into a single one. Without this function, users who switch from one domain to another are counted as separate sessions and users. In addition, conversion events (key events) cannot be assigned to a user across multiple domains.
Cross-domain tracking is indispensable for companies with separate checkout or booking platforms or for groups with several brands. It provides a clear overview of traffic, engagement and web performance.
It is particularly important for the evaluation of cross-domain A/B tests.
How to set up cross-domain tracking for GA4
Installation of cross-domain tracking in GA4
Setting up cross-domain tracking in GA4 is much easier compared to Universal Analytics, as the entire configuration is done within GA4. Here is a detailed guide on how to set up cross-domain tracking in just a few steps:
Step 1: Make sure that GA4 is installed on both websites
- Both websites must use the same GA4 property.
- Implement the GA4 tracking code either directly in the page source code (via
gtag.js) or via the Google Tag Manager (GTM). - Make sure that the GA4 code is correctly integrated on all pages and that the data is sent to the same property.
Step 2: Configure domains for cross-domain tracking
1. log in to your GA4 account and go to Admin.
2. select under Data collection settings the point Data streams.
3. select the corresponding data stream (e.g. "Website stream").
4. scroll down to Configure tag settings and click on it.
5. go to Configure your domains.
Add the domains you want to track (e.g. domain1.com and domain2.com).
- Enter the URLs without a prefix such as
https://. - GA4 will automatically treat these domains as belonging together and link the data.
Step 3: Ensure URL parameters for user tracking
- GA4 uses the URL parameter
_glto transfer information such as client ID and campaign data when switching between domains. - This parameter is added automatically if cross-domain tracking is set up correctly.
- Check whether the
_gl-parameter appears in the URL when a user navigates between the two domains.
Step 4: Using Google Tag Manager (optional)
If you use Google Tag Manager, you can also set up cross-domain tracking there:
Adjust tags:
- Open the Google Tag Manager and go to Tags.
- Select the GA4 configuration tag that is used on both domains.
- Go to the advanced settings and activate Automatic link tagging under Cross-domain tracking.
- Add the domains that are to be linked.
Check trigger:
- Make sure that your tags are configured so that they are triggered on all relevant pages (e.g. "All pages").
Activate preview mode:
- Test your setup in the Tag Manager preview mode. Navigate between the domains and check whether the
_gl-parameter is transferred correctly.
- Test your setup in the Tag Manager preview mode. Navigate between the domains and check whether the
Step 4: Test and check
Navigate between the two domains and check in GA4:
- Are sessions and users tracked consistently across both domains?
- Is the traffic correctly assigned and not displayed as "referral traffic" between the two domains?
The navigation between the domains should appear seamless in the reports.
Advantages of cross-domain tracking with GA4
With cross-domain tracking in GA4 you can:
- Trace the user path across multiple domains.
- Correctly aggregate sessions, conversions and events.
- Ensure that Analytics reports are not distorted by incorrect referrals or duplicate sessions.