Full Answer
GA4 and Facebook numbers will never match perfectly—and they shouldn't. Each platform uses fundamentally different attribution models, counting methodologies, and data collection approaches. A 10-30% discrepancy is normal and expected. The Five Reasons Numbers Differ 1. Attribution Windows Facebook Ads Manager:
- Default: 7-day click, 1-day view
- Counts conversions that happen within 7 days of clicking an ad
- Also counts conversions within 1 day of viewing an ad (view-through)
- You can customize windows (1-day, 7-day, 28-day combinations) GA4:
- Default: 90-day click attribution
- Doesn't track view-through conversions from ads
- Much longer attribution window means more conversions attributed to older traffic sources Example: User clicks Facebook ad on Monday, purchases on Wednesday:
- Facebook counts it (within 7-day click window)
- GA4 counts it (within 90-day window) User clicks Facebook ad on Monday, purchases 10 days later:
- Facebook doesn't count it (outside 7-day window) -...