// glossary
Conversion Tracking.
Measurement infrastructure
Conversion tracking is the process of measuring the conversions (purchases, signups, leads, downloads) produced by digital ad campaigns. Faulty conversion tracking corrupts every downstream optimization — the algorithm gets fed phantom signals and optimizes for the wrong outcome.
// detail
Common problems:
- Double-counting — Tag Manager trigger duplicated
- Missing fires — some conversions go uncaught
- GA4 ↔ Google Ads mismatch — 10%+ gap between the two measurement systems
- Cross-domain breaks — payment page on a different domain truncates session
- iOS 14+ losses — App Tracking Transparency weakened iOS conversion signal
Verification: Tag Assistant + Google Ads ↔ GA4 cross-check + server-side GTM (if used) request log review.
Example: An e-commerce account where Google Ads reports 50 conversions while GA4 reports 35 has a 30% gap. Optimizing without diagnosing the source (cross-domain, double-count, attribution diff) produces wrong results.