Resolving GA4 Data Discrepancies for Google Ads
📌Introduction
A performance marketing agency noticed their Google Ads conversion numbers were significantly higher in GA4 than in the Google Ads dashboard, causing budgeting decisions based on inaccurate data.
❗The Problem
GA4 was counting conversions using a different attribution model and session timeout window than Google Ads, resulting in a 35% discrepancy. The client was over-reporting conversions and misallocating ad spend across campaigns.
🔍Identifying the Causes
After a full audit, we identified three root causes: (1) GA4 was using data-driven attribution while Google Ads used last-click, (2) Session timeouts were set differently between platforms, (3) Cross-device journeys were not being stitched correctly due to missing User ID implementation.
⚠️Consequences for the Business
The business was allocating 40% more budget to top-of-funnel campaigns believing they were converting, while bottom-funnel campaigns were being under-funded. This led to wasted ad spend and missed revenue targets for two quarters.
✅Solution
We aligned attribution models across both platforms, implemented User ID tracking via GTM to enable cross-device stitching, synchronized session timeout settings, and created a reconciliation Looker Studio report comparing both data sources side by side.
📈Results
Data discrepancy dropped from 35% to under 4% within 30 days. The client reallocated budget to high-performing campaigns and saw a 22% improvement in ROAS within 6 weeks. Decision-making confidence in data improved significantly.
🏁Conclusion
Data discrepancies between GA4 and Google Ads are common but fixable. Aligning attribution settings and implementing cross-device tracking is essential for accurate performance measurement.
💡Key Takeaways
Always audit attribution models when comparing platforms. User ID tracking is critical for cross-device accuracy. A reconciliation dashboard helps catch future drift early.