Server-side tracking is no longer optional

What is causing the data loss

A compounding set of factors: ad blockers (now used by an estimated 30% of European desktop users), Apple's ITP and ATT frameworks, Firefox and Safari tracking-prevention defaults, EU consent regimes that reduce cookie scope, and bots and scrapers that pollute browser-side measurement.

Each factor on its own is manageable. Combined, the result for browser-only setups is conversion data that systematically under-reports — and, more dangerously, under-reports unevenly across channels.

How server-side measurement fixes it

Tools like Google's Conversion Linker, Meta's Conversions API, TikTok's Events API, and server-side Google Tag Manager move data collection from the browser to a controlled server environment. Conversions are sent to platforms in a way that is robust against the issues above — and consistent across channels.

The setup is meaningful but not enormous: a typical implementation takes two to four weeks for a single brand or destination. The return is more accurate data, better-performing bidding strategies, and a measurement setup that survives the next browser update.