Definition
Cross-domain tracking connects user sessions across multiple domains (for example marketing site -> checkout) to preserve attribution and funnels.
Example
Users move from marketing.site.com to checkout.site.com without losing the original source.
How to use it
- Ensure linker parameters pass across redirects and payment providers.
- Test end-to-end after changes to checkout, routing, or domains.
- Align cookie domain settings so sessions do not reset across subdomains.
Common mistakes
- Breaking attribution by stripping query parameters on redirects.
- Letting self-referrals inflate new sessions and distort ROAS in analytics.
- Changing domains without updating linker configuration.
Measured as
Measure Cross-domain Tracking with a fixed attribution window, conversion event, and spend basis before comparing campaigns or creative tests.
Misused when
- Breaking attribution by stripping query parameters on redirects.
- Letting self-referrals inflate new sessions and distort ROAS in analytics.
- Changing domains without updating linker configuration.
Operator takeaway
- Ensure linker parameters pass across redirects and payment providers.
- Test end-to-end after changes to checkout, routing, or domains.
- Align cookie domain settings so sessions do not reset across subdomains.
- Use Cross-domain Tracking only inside a stable attribution rule, conversion definition, and time window so campaign comparisons stay honest.
- If performance changes, check whether the metric moved for a real business reason or because the measurement setup changed underneath you.
Next decision
- Read UTM + GA4 attribution: practical tracking for paid ads (without lying to yourself) if the decision depends on interpretation, policy, or trade-offs beyond the raw formula.
- Decide which report owns Cross-domain Tracking before comparing campaigns, channels, or creative tests.
Where to use this on MetricKit
Guides
- UTM + GA4 attribution: practical tracking for paid ads (without lying to yourself): A practical guide to UTMs and GA4: consistent source/medium/campaign tagging, conversion deduplication, and common attribution traps.