Cross-Domain Tracking

Cross-domain tracking connects a visitor journey that spans two independent websites — two Properties — so a conversion on the destination domain (a hosted checkout, booking engine, or second funnel domain) attributes back to the ad click that landed on the source domain. The click ID travels on cross-domain links via the atrefid parameter, added at click time.

Where cross-domain tracking settings live

Everything is configured on the source Property (where the ad click lands):

the destination domains list;
the Sync Conversions toggle (synced conversions default to Purchase, InitiateCheckout, ViewContent, AddToCart, AddPaymentInfo);
the UTM AutoTag option for carrying campaign parameters across.

With Sync Conversions ON, cross-domain links carry atrefid; with it OFF, they carry the atclid.

When you do NOT need cross-domain tracking

Subdomains of one root domain (www.example.com, shop.example.com) share the first-party cookie — they belong in one Property with no cross-domain setup. Recommending cross-domain for a same-root-domain funnel is a common support error.

Cross-domain Properties and deduplication

The recommended setup for two real domains is two Properties + cross-domain tracking — do not consolidate into one Property. AnyTrack does not deduplicate across Properties: with the same Meta pixel on both, the conversion-side Property sends 100% of its conversions and syncs originated ones back to the source Property, which sends them again — so Events Manager over-counts while Ads Manager still attributes correctly. This is expected behavior, not a bug. Also check for the conversion dead end: a Property that records purchases but has 0 pixels connected sends nothing anywhere — the fix is cross-domain tracking from the source Property, not connecting the ad platform to the checkout Property (the click never touched it).

Frequently asked questions

FAQ was last reviewed on 2026-08-01

My pages are on shop.example.com and www.example.com — do I need cross-domain tracking?

No. Subdomains of the same root domain share the first-party cookie: use one Property and no cross-domain setup. Cross-domain tracking is for two independent root domains.

Should I merge two domains into one Property instead of setting up cross-domain tracking?

No — the recommended setup is two Properties connected with cross-domain tracking; it guarantees accuracy. Each Property is a separate business context with its own integrations and pixels.

With the same Meta pixel on both Properties, will conversions be double-counted?

Meta's Events Manager will over-count, because the conversion-side Property sends all its conversions and syncs originated ones back to the source Property, which also sends them. That over-count is expected; Ads Manager still attributes correctly. AnyTrack does not deduplicate across Properties.