The 18% of conversions that ad blockers ate

The 18% of conversions that ad blockers ate

A lead-gen site noticed its analytics conversions never matched its CRM. The CRM had more deals than the tracker recorded. The gap was the blocked tag.

Client-side tracking runs in the browser, where ad blockers, privacy modes and slow scripts quietly drop events. The clue: the discrepancy was largest on technical-audience pages, exactly where ad-block rates run highest.

The change: we moved the key conversion event to a server-side endpoint that fired from the backend on form submit, independent of the browser.

Recorded conversions jumped 18% overnight, not because more people converted, but because the blocked ones were finally counted, and the tracker matched the CRM to within 3%.

Client-side tagging is easy and lossy. Server-side is harder and honest. For the events you bill against, measure where the blockers can't reach, on your own server.