How do I check if my GA4 has Cross-Domain Tracking configured correctly?

Run a free NiceLookingData audit on your GA4 property. The audit runs 58 checks across configuration, data quality, measurement, compliance, and optimization — including any rule that touches Cross-Domain Tracking — and emits plain-English findings in 60 seconds.

Definition · GA4 Glossary

What is Cross-Domain Tracking?

A configuration that allows GA4 to pass identifiers across different domains, ensuring a single user journey isn't split into two separate sessions.

When a user clicks a link from your main website (shop.com) to a third-party checkout or portal (secure-checkout.com), their browser considers them a completely new visitor because cookies cannot be read across different domains.

Cross-domain tracking solves this by appending a special URL parameter (the _gl parameter) to the destination link. When the user lands on the second domain, GA4 reads that parameter and stitches the two sessions together.

The symptoms of broken cross-domain tracking:

If you haven't set this up correctly, you will experience:

Inflated User/Session counts: Because every crossing is counted as a new user.
Self-Referrals: Your main domain will show up in your reports as the referring traffic source for the conversions that happen on the second domain.
Broken Attribution: The original traffic source (e.g., a Facebook Ad) gets lost, and the conversion is attributed to "Referral".

A GA4 audit tool like NiceLookingData checks exactly for these domain mismatches and missing _gl parameters.

From definition to diagnosis

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Related terms.

First-Party Cookie

A tracking cookie created and read only by the exact domain the user is currently visiting.

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