Troubleshooting Data Discrepancies Between Universal Analytics and GA4

Data discrepancies between Universal Analytics (UA) and Google Analytics 4 (GA4) are common and primarily arise due to fundamental differences in their data models and measurement approaches. UA uses a session-based model, grouping user interactions into sessions, whereas GA4 uses an event-based model, tracking each interaction as a separate event. This leads to inherent differences in how data like sessions, users, and conversions are counted.

Key reasons for discrepancies include:

• Different data models: UA sessions vs. GA4 events cause differences in event counts and session metrics.
• Estimation in GA4: GA4 uses machine learning to estimate user and session metrics, which can cause variations compared to UA's raw counts.
• Scope and metric mismatches: Querying data on different scopes (user, session, event) or using different dimensions and metrics can produce seemingly conflicting results.
• Enhanced measurement and cross-device tracking: GA4 tracks users across devices more comprehensively, which can alter user counts compared to UA’s device-specific tracking.
• Privacy and data retention: GA4 includes privacy features like consent mode and data deletion that can affect data availability and counts.

To troubleshoot and minimize discrepancies:

1. Understand the data model differences and adjust expectations accordingly.
2. Ensure consistent metric and dimension selection when comparing reports or exporting data.
3. Compare equivalent events and conversions carefully, especially when migrating from UA to GA4 key events.
4. Check for implementation issues such as missing tags or incorrect event setup that could cause data loss or inflation.
5. Use GA4’s debug and real-time reports to verify event collection accuracy.
6. Be aware of GA4’s estimation and sampling, which can cause minor differences even within GA4 reports.

By recognizing these inherent differences and carefully aligning your reporting queries and event setups, you can better interpret and reconcile data discrepancies between UA and GA4.