Full Answer

The logic is straightforward: every A/B test, every checkout tweak, every landing-page experiment relies on conversion data to declare a winner. If that data is missing 30–40% of events — which is the documented loss rate from ad blockers, browser privacy restrictions, and consent rejection — the test results are unreliable. A variant might look like a winner because it happened to retain more trackable visitors, not because it actually converted better.

WooCommerce stores face this problem acutely because the default tracking setup runs entirely client-side. Every pixel, every GA4 tag, every Meta CAPI browser event fires from JavaScript that ad blockers can suppress. The store owner sees a conversion rate in GA4, but it's calculated from an incomplete numerator and an incomplete denominator — both wrong, in different directions.

Server-side tracking captures the events at the server before they ever touch a browser, which means the data survives ad blockers, ITP cookie caps, and consent rejection for analytics-only processing. Once the numbers are trustworthy, optimisation actually works — you know the real baseline, you can measure real lifts, and you stop investing in changes that only looked good on broken data ([server-side tracking for WordPress](https://seresa.io/blog/server-side-tracking-wordpress/)).