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Implementing Cross Domain Tracking with Multiple GTM Containers in GA4
Hey, I’m looking to create cross domain tracking for a pair of domains (hypothetically, website A and B).
- Both websites have their own GTM setups with a nice mix of custom events.
- They also each have individual GA4 properties (they’re not the same one) that come with unique data streams that funnel data to GA4 through GTM.
The big G’s official documents say I need the same data stream for each domain before I set up cross domain tracking in GA4. But, I don’t want to start blending data from two separate websites into one existing property. So, what’s the game plan here? Is there a way we can direct data into the same data stream without creating a data smoothie?
Maybe we could create a fresh GA4 property and pop a config tag in both GTM containers (for website A and B) with a matching Measurement ID. Should this tag only be added to the event triggered by a click on an outbound link from domain A?
And what about poor old domain B? Do we assign a config tag with a new data stream to all events flaring up from page views?
I’d appreciate any and all advice or guidance. Thanks a bunch!
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2 Replies
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Creating a fresh GA4 property for both Website A and Website B to use, and then adding a Config Tag in both GTM containers with a matching Measurement ID, could indeed work for your situation if you don’t want to blend data from the two sites. For Website A, the tag would be triggered by a click on an outbound link to Website B. For Website B, a Config Tag with a new data stream would be assigned to all events from page views, thus completing the cross-domain tracking setup. This gives you a setup where the domains share data streams without mixing the data from the two sites in a way that you don’t want.
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Cross-domain tracking in GA4 can be a bit tricky with separate GTM and GA4 setups. The official documentation notes that you need a shared data stream, as it helps Google Analytics understand that user interactions across the two domains are from the same user session. However, this doesn’t necessarily mean you need to blend your data.
Creating a new GA4 property for cross-domain tracking could be effective. You’d want to add a config tag with the new measurement ID to both GTM containers. The idea here is to have a separate stream of data that’s only for cross-domain tracking. You don’t need to limit this tag to only the event triggered by a click on an outbound link from domain A. It should track all user interactions across both domains.
For domain B, and also for domain A, you should certainly assign the config tag with the new data stream to all events. This will enable GA4 to follow the user as they move between the two domains and build a complete picture of their behavior. Again, this doesn’t necessarily mean that you’re blending your existing data. You’re just creating a supplementary stream that specifically tracks users who move between the two domains.
Remember, you aren’t losing any of the individual data from each website setup. This data is still tracked individually by each domain’s unique GTM and GA4 setup. The new GA4 property is in addition to, not in place of, your existing setups. It’s simply a way to give you insight into user behavior that spans both domains. Just make sure to keep all your events, conversions and other configurations consistent between the domains.
If you still have queries or run into issues, don’t hesitate to seek advice from a GA4 implementation specialist or attend one of Google’s dedicated training sessions.
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