Consent Mode.

Consent Mode is a Google framework (implemented via Google Tag Manager or gtag.js) that dynamically adjusts how Google Analytics, Google Ads, and other Google tags operate based on a user's cookie consent decisions. When a user declines cookies, Consent Mode v2 prevents full measurement tags from firing — respecting consent — but fires cookieless pings that feed Google's modelling algorithms to estimate the behaviour of non-consenting users.

Consent Mode v2 and the EU

In 2024 Google made Consent Mode v2 mandatory for advertisers using Google's EU consent frameworks (GDPR). Two new parameters — ad_user_data and ad_personalization — control whether data can be used for ad personalisation beyond measurement. Without implementing Consent Mode v2, EU advertisers risk losing access to Smart Bidding signals and conversion modelling for European traffic.

How Modelled Conversions Work

When consent is withheld, Consent Mode v2 fires minimal cookieless pings — timestamps, rough geo data, conversion event type — which Google uses alongside consenting users' patterns to model the behaviour of non-consenting users. This modelled data is added back into Google Ads and GA4 reporting as 'modelled conversions', recovering some of the signal lost to consent refusal. Accuracy depends on having a sufficiently large consenting user base to model from.