Q: How do I set up cross-domain tracking so my checkout domain isn't counted as a referral?

Q: How do I set up cross-domain tracking so my checkout domain isn't counted as a referral?
A: GA4 stitches sessions by passing _gl in the link. Configure it here:
— Admin → Data Streams → your web stream → Configure tag settings → Configure your domains.
— Add every domain (e.g. shop.com and checkout.com) with the 'contains' match type.
— Add the payment/checkout host to Admin → Data Streams → 'List unwanted referrals' so it stops opening new sessions.
— Verify: click between domains, check the URL carries ?_gl=, then watch one continuous session in Realtime.
TL;DR: List both domains under cross-domain config and exclude the checkout host as a referral — sessions then stay whole.
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