Full Answer
Client-side tracking depends on a fragile chain: JavaScript has to download, execute, fire before navigation, and reach a third-party endpoint without being blocked anywhere along the way. Each link is a failure point. Ad blocker usage sits at 15-30% globally and over 40% in some North American markets, and Apple's Intelligent Tracking Prevention strips third-party cookies in Safari by default. Server-side tracking uses PHP hooks like woocommerce_payment_complete that fire on the server regardless of the visitor's browser, so the only thing between the event and the destination platform is your own server.
