GA4 · CAPI · Sync
Which number is true?
Why Discrepancies Are Normal
GA4 measures sessions and conversions using its own logic. Meta CAPI measures based on the Meta attribution window. Differences arise from conflicting view-vs-click logic, time windows, and user ID matching. A 22 to 38% discrepancy is normal; anything above that is critical.
01
22-38%
Normal Discrepancy
02
CRM
Single Source of Truth
03
User ID
Cross-Reference Key
How to Build the Cross-Reference
- User ID in both systems (GA4 and Meta CAPI)
- CRM as the single source of truth, reconciled against both tools
- Custom events with a consistent naming convention
- Weekly reconciliation reporting
Example
Brands that use CRM as the single source of truth end the reporting war between marketing and finance. Both teams look at the same numbers; GA4 and Meta are simply sub-layers.
When Discrepancy Becomes Critical
A discrepancy above 50% between GA4 and Meta means one of the two is broken. Double-firing pixels, server-side setup errors, user ID mismatches. An audit is mandatory. Below 22% is normal; anything in between is the watch zone.
„Every tool lies a little. CRM is the truth.”