What is Cross-Domain Tracking?
TL;DR
Configuring analytics to track users across multiple domains as a single session. If your main site is example.com but checkout happens on shop.example.com (or a different domain entirely), standard Google Analytics 4 sees these as separate visitors. Cross-domain tracking links them, preserving the user journey across domains. Without it, you can't properly attribute conversions to their original sources, someone from your Google Ad appears as "direct" when they reach the checkout domain. Configure cross-domain tracking in GA4 Admin under Data Streams → Configure tag settings. This requires technical implementation and testing. If you use Shopify's checkout, a separate scheduling platform, or any third-party tool on a different domain, investigate whether cross-domain tracking is needed for accurate attribution.
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Frequently Asked Questions About Cross-Domain Tracking
When do I need cross-domain tracking?
When visitors move between different domains during their journey, main site to external checkout, to a scheduling tool on a subdomain, or to a separate cart system. If any conversion happens on a different domain, you probably need it.
What happens without cross-domain tracking?
A visitor from your Google Ad goes to your site, then to external checkout. Analytics sees two separate visitors. The conversion gets attributed to 'direct' instead of Google Ads. You can't measure true marketing ROI.
How do I set up cross-domain tracking in GA4?
Go to Admin → Data Streams → select your stream → Configure tag settings → Configure your domains. Add all domains in the user journey. Test thoroughly, misconfiguration causes duplicate sessions and broken attribution.
Does cross-domain tracking work with Shopify checkout?
Shopify checkout uses a different domain. You need to configure cross-domain tracking in GA4 to link the journey. Some Shopify GA4 apps handle this automatically; verify your setup by testing the full purchase flow.
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