Full Answer

When you implement Advanced Consent Mode and a visitor declines cookies, GA4's Google tag still fires — but in a restricted mode. The tag sends a cookieless ping that strips all identifying information. No _ga client ID is set. No first-party cookies are created. No user properties or custom event parameters are transmitted. What reaches Google is a shell: a timestamp, a randomised session identifier, the referrer, and device-level metadata like browser type and screen resolution.

GA4 cannot link one ping to another from the same user. A single visitor moving through five pages generates five disconnected pings that GA4 treats as potentially five separate interactions. There is no session stitching, no return-visitor recognition, and no conversion path reconstruction for these users.

Behavioural modelling takes the patterns observed in the consenting cohort and projects them onto the distribution of cookieless pings. If 8% of consenting users who view a product page eventually purchase, GA4 estimates that a similar percentage of non-consenting users probably did the same. These modelled conversions appear in your standard reports alongside measured conversions — and GA4 does not separate them into distinct columns by default.

Google's own documentation states that modelling requires at least 1,000 daily consented events for 7 of the past 28 days and 1,000 daily denied events for 7 consecutive days. Most WooCommerce stores with fewer than 30,000 monthly visitors do not meet these thresholds, meaning modelling never activates — and the cookieless pings produce no usable output at all.