Full Answer

The revenue gap between GA4 and WooCommerce is not a bug — it is the predictable result of running measurement through a browser script that five independent forces are working to block. Putler's 2026 data puts the typical undercount at 10-20%, but stores with heavy European traffic or privacy-focused audiences can see gaps above 30%.

Ad blockers are the single largest factor. With 52% of consumers running one, roughly half of all sessions never fire the GA4 tag at all. EU consent banners compound the loss: rejection rates between 40% and 70% mean a further slice of traffic opts out before the script loads. Safari's Intelligent Tracking Prevention then caps any first-party cookie to seven days, fragmenting returning-visitor attribution even when the tag does fire.

The last two causes are checkout-specific. Cross-domain redirects — common with hosted payment pages — break the GA4 session, and gateway-side redirects can complete a purchase before the thank-you page (and its purchase event) ever loads. Server-side tracking resolves all five by capturing events at the server layer, where ad blockers, consent banners, and cookie caps have no reach. Pairing it with a weekly reconciliation routine between GA4 and WooCommerce order data surfaces the remaining drift before it compounds into a full reporting quarter of bad data.