Implement cross-domain tracking in GA4 using linker parameters to maintain session continuity, fix attribution, and track users across multiple domains.
AI Summary
Quick Overview
Implement cross-domain tracking in GA4 using linker parameters to maintain session continuity, fix attribution, and track users across multiple domains.
Do I need cross-domain tracking for subdomains?
Cross-domain tracking in GA4 lets you follow users as they navigate between multiple domains, preventing session breaks and attribution loss. Whether you use a separate checkout domain, external payment processor, or multiple subdomains, proper cross-domain setup is critical for accurate analytics.
Why Cross-Domain Tracking Matters
Without cross-domain tracking, users navigating from yoursite.com to checkout.stripe.com appear as two separate sessions. The conversion gets attributed to "direct" traffic instead of the original source, destroying your attribution data.
- Session continuity: Maintain single session across domains
- Attribution accuracy: Credit the original traffic source
- User journey visibility: See complete path to conversion
- Reduce false "direct" traffic: 30-50% of "direct" conversions are actually cross-domain breaks
Common Cross-Domain Scenarios
- Separate checkout domain: yoursite.com → checkout.yoursite.com
- Third-party payment: yoursite.com → checkout.stripe.com → yoursite.com/thanks
- Multiple brand domains: brandA.com → brandB.com
- Subdomain navigation: www.site.com → shop.site.com → blog.site.com
How GA4 Cross-Domain Tracking Works
GA4 uses linker parameters to pass client_id between domains. When a user clicks a link to a configured domain, GA4 appends ?_gl=XXXXXXXXX to the URL. The destination domain reads this parameter and continues the same session.
Configure Cross-Domain Tracking
Method: Google Tag Manager (Recommended)
Testing Cross-Domain Tracking
- Enable GA4 DebugView
- Navigate to yoursite.com and note client_id
- Click link to checkout.yoursite.com
- Verify URL includes ?_gl=... parameter
- Check client_id matches on second domain
- Trigger conversion event
- Verify attribution credits original source, not "direct"
Common Issues
Linker Parameter Not Appearing
Cause: Domain not in linker configuration, or gtag.js not loaded before link click. Fix: Verify domains array includes both source and destination domains.
Different client_id on Second Domain
Cause: Destination domain doesn't have GA4 tracking, or has different Measurement ID. Fix: Ensure ALL domains use same Measurement ID and have linker configured.
Do I need cross-domain tracking for subdomains?
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