Full Answer

Detecting UTM stripping requires testing at three layers: manual link testing, GA4 diagnostic reports, and platform-to-platform comparison. Each catches different types of stripping that the others miss.

Manual testing is the most reliable starting point. Copy a full campaign URL with all UTM parameters intact, open an incognito browser window to eliminate cached redirects, paste the URL, and carefully watch the address bar through every redirect hop. Note whether the parameters survive each transition. Common stripping points include 301/302 redirects in htaccess rules that drop query strings, CDN or caching layer redirects that strip parameters for cache key simplification, and URL shorteners configured to truncate query strings.

GA4 diagnostic indicators provide an ongoing monitoring layer. Navigate to Traffic Acquisition and examine the Unassigned and Direct channels. A sudden spike in either — particularly if it coincides with a campaign launch, redirect change, or CDN configuration update — strongly suggests UTM parameters are being stripped somewhere in the delivery chain. The timing correlation between infrastructure changes and attribution data shifts is often the clearest signal.

Platform comparison delivers the quantitative measure. Export click counts from your ad platforms for a given campaign period, then compare against GA4 sessions carrying the matching utm_source and utm_campaign values. The ratio between platform clicks and attributed GA4 sessions should exceed 85%. Below that threshold indicates systematic loss worth investigating.