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Why do my GA4 and Facebook numbers never match?

ga4 facebook numbers dont match platform attribution mismatch facebook vs google analytics conversion tracking discrepancy attribution window differences

Quick Answer

Different attribution windows (Meta: 7-day click/1-day view vs GA4: session-based last-click), view-through conversions (Meta counts ad impressions, GA4 doesn't), cross-device tracking gaps, cookie consent differences, and conversion modeling where platforms estimate conversions from opted-out users. A 10-15% discrepancy is normal. The fix isn't making them match -- it's using your own data warehouse or CRM as the single source of truth and treating platform numbers as directional estimates for optimization, not absolute counts.

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) -...

Sources

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Cherry Tree by Seresa - https://seresa.io/seed/utm-attribution/_archive-platform-numbers-mismatch