GA4 vs Meta Attribution: Which Numbers Should You Trust?
Your GA4 and Meta Ads Manager will almost never agree on conversions. Here's why that happens and how to build a reporting model you can trust.
If you've ever compared your GA4 data with your Meta Ads Manager, you've probably noticed they never agree. This isn't a bug, it's a fundamental difference in how each platform measures conversions.
Why the Numbers Don't Match
1. Attribution Windows
GA4 uses a last-click, session-based model by default. Meta uses a 7-day click, 1-day view window. Someone could click your ad on Monday, come back via Google search on Wednesday, and convert. GA4 credits Google; Meta credits itself.
2. Conversion Counting
GA4 can be set to count one conversion per session or one per event. Meta counts every conversion within its attribution window. Same user, different numbers.
3. Cross-Device Tracking
Meta has strong cross-device tracking because users are logged in. GA4 relies on cookies and Google Signals, which have gaps, especially on iOS.
Building a Trustworthy Reporting Model
The solution isn't to pick one platform over the other. Instead, build a unified measurement framework. Use GA4 as your source of truth for web analytics, use platform data for optimisation signals, and reconcile with server-side conversion data for the real picture.
At AlphaTrack Digital, we build custom Looker Studio dashboards that pull from multiple sources and present a single view of truth. No more guessing which number is right.
