Attribution Windows Explained: Why Your Ad Platform and Analytics Disagree

It's one of the most common sources of confusion in paid media: Meta reports one number for conversions, GA4 reports a different one, and both dashboards are technically telling the truth. The disagreement comes down to attribution windows and modeling, not fraud or error.

Different platforms count differently

Meta's default attribution window includes both click-through and view-through conversions within a set timeframe, while GA4 typically leans more heavily on last-click, session-based attribution. These are fundamentally different counting methods, so an exact match was never realistic.

Which number should you trust?

Neither number in isolation. The more useful approach is to pick one system as your primary source of truth for day-to-day optimization decisions, and use the other as a directional sanity check rather than expecting them to reconcile.

What actually matters more

Trends matter more than absolute numbers here. If both platforms show a campaign improving or declining in the same direction over time, that's a far more reliable signal than trying to force two different attribution models to agree on an exact conversion count.