Why Google Ads, Meta, and GA4 never agree on conversions

A common early conversation with a new client involves a discrepancy: Google Ads reports one conversion count, Meta reports another, and GA4 reports a third, all for the same time period. None of them is necessarily wrong — they're using different attribution windows, different identity resolution methods, and sometimes different definitions of what counts as a conversion.

Google Ads and Meta each attribute conversions using their own view of the user's journey, generally favouring their own platform's touchpoint. GA4 applies its own model across all channels, which can credit a conversion differently again. Add in view-through versus click-through counting, and default attribution windows that differ by platform, and the disagreement is structural, not accidental.

The fix isn't to force all three numbers to match — they measure genuinely different things and never fully will. The fix is to designate one source of truth for business reporting (often a server-side or CRM-verified conversion count) and treat the platform-reported numbers as directional signals for in-platform optimisation only.

Document which number means what, and who uses it for which decision. A lot of internal disagreement about 'what the numbers say' disappears once everyone knows which of the three systems they're actually looking at.