Full Answer

Ad blockers and consent banners both reduce tracking coverage, but they operate through different mechanisms and at different scales.

Ad blockers are browser extensions or DNS-level filters that prevent known tracking domains and scripts from loading. They affect 15–25% of visitors depending on the market and audience demographic. Crucially, ad blockers are binary per visitor — a user either has one or does not. And ad blocker technology targets specific scripts, meaning server-side tracking that operates through first-party infrastructure can bypass most ad blocker rules.

Consent banners, mandated by GDPR, ePrivacy, and similar regulations, present a legal choice to every visitor. When a visitor rejects non-essential cookies, the consent management platform must suppress all tracking that relies on cookie-based identification — which includes GA4's client ID, Facebook's fbp and fbc cookies, and any conversion tag that writes or reads browser storage. Rejection rates of 30–45% are common, and in privacy-conscious markets like Germany and the Netherlands, rates above 50% are documented.

The compounding effect is significant. A WooCommerce store in a regulated market may lose 30–45% of visitor data to consent rejection and an additional 15–25% of the remaining consented visitors to ad blockers. The combined tracking gap can exceed 50% of actual site activity.

Server-side tracking reduces the ad blocker gap by moving data collection to the server. But consent rejection requires a different approach: cookieless measurement, modelled conversions, or consent mode v2 implementations that send anonymised pings for non-consented users. The consent problem is legal, not technical — and it demands a data strategy that accounts for permanent partial blindness rather than assuming full visibility.