Full Answer

The mechanism is simple: ad blockers maintain filter lists — EasyList, EasyPrivacy, uBlock Origin's default lists — that match known tracking domains and script paths. When a page loads, the blocker checks every network request against these lists. Requests to google-analytics.com, connect.facebook.net, googletagmanager.com, and similar endpoints are silently cancelled before the script downloads. No script means no dataLayer push, no event dispatch, no conversion recorded. The WooCommerce order completes through PHP on your server, completely independent of whether the browser ran any JavaScript.

The data loss compounds across the funnel. If a visitor's first session was blocked, you have no acquisition source. If their add-to-cart was blocked, your funnel analysis shows a drop that never happened. If their purchase was blocked, your GA4 revenue is lower than your WooCommerce total and your ad platform cannot attribute the conversion back to the campaign that drove it. The campaign looks worse than it performed, bidding algorithms get weaker signals, and budget shifts away from channels that are actually converting.

Server-side tracking sidesteps this entirely. When the purchase event fires from your web server via the GA4 Measurement Protocol or Meta Conversions API, the ad blocker in the visitor's browser has no opportunity to intervene — the request never touches the browser. For a full breakdown of the scale of this problem, see how 912 million ad blocker users are hiding a third of WooCommerce traffic.