GA4 vs Meta Discrepancy: Which Number Should You Trust?

GA4 and GTM · 4 min read · by Anna Viggeborn

Meta and GA4 disagreeing is normal. They use different attribution models, different identity signals and different conversion windows. A difference does not prove either one is broken.

Why they differ by design

• Meta credits clicks and views within its own attribution window. GA4 uses its own model, by default data driven.
• Meta can match logged in users across devices. GA4 relies on its own identity space.
• Meta reports conversions on the day of the ad interaction. GA4 reports on the day of the conversion.
• Meta includes its own server events. GA4 mostly sees the browser.

When the gap is a real signal problem

• The gap changed sharply from one week to the next with no campaign change.
• One platform moved and the other did not, while your orders stayed flat.
• The change lines up with a release, a consent update or a checkout change.
• Meta reports more purchases than your store recorded at all.

How to use both

Use the platform to steer the platform, and your own order data to judge the business.