The essentials
- Definition: Consent Mode is the mechanism through which a site passes the user's cookie choice to Google's services, so that data collection adapts accordingly.
- Version 2: mandatory since March 2024 in the European Economic Area to keep using Google Ads audiences and conversions; it adds two advertising-related signals.
- Modelling: Google estimates the conversions of visitors who refused cookies from the behaviour of those who consented; it recovers 30 to 70% of the lost conversions, depending on volume.
- Without Consent Mode: conversions from refusals are lost, audiences empty out, and automated bidding optimises on incomplete data.
The aim of Consent Mode is the mechanism through which a website passes the user's cookie choice to Google's tags. Rather than blocking the tags entirely when the visitor refuses, the site loads them in a degraded state: they send an anonymous signal, with no identifier and no cookie, which lets Google measure a volume without identifying the person. It is Google's answer to the interplay between the GDPR, the ePrivacy directive and advertisers' need to measure. The general obligations are set out in GA4 and the GDPR.
The four signals of version 2
| Signal | What it allows | Introduced in |
|---|---|---|
analytics_storage | Audience measurement cookies (GA4) | Version 1 |
ad_storage | Advertising cookies (remarketing, conversions) | Version 1 |
ad_user_data | Sending personal data to Google for advertising purposes | Version 2 |
ad_personalization | Ad personalisation and remarketing | Version 2 |
Version 2 has been required since March 2024 for any site advertising to users in the European Economic Area. Without it, Google Ads stops feeding remarketing audiences and customer lists, and some conversions are no longer attributed.
Basic mode and advanced mode
- Basic mode: Google's tags don't load until the visitor has accepted. No data is sent if they refuse, so no modelling is possible. This mode is the most protective and the easiest to defend legally.
- Advanced mode: the tags load on arrival and send cookieless signals (anonymous pings) until the choice is made, then adapt. It enables conversion modelling and gives a more complete measurement, at the cost of a continuing debate about its compliance between national authorities.
The choice is a trade-off between measurement quality and legal caution; in France, the data protection authority requires that no cookie be set before consent, which advanced mode respects, since it writes nothing until the choice is given.
What modelling recovers
When a visitor refuses cookies, Google can no longer connect their ad click to their purchase. Modelling fills that gap: from the observed behaviour of consenting visitors, a model estimates how many conversions the refusals probably produced and adds them back into the reports. The recovery rate depends on volume: a site with more than 1,000 ad clicks and 100 conversions a month recovers 50 to 70% of the lost conversions; below those thresholds, modelling doesn't kick in at all. In France, where 25 to 40% of visitors refuse cookies, the gap between raw measurement and reality is considerable, which directly affects the automated bidding described in Smart Bidding.
Setting up Consent Mode
- Choose a certified CMP: a consent management platform that is a Google partner, and passes the four signals automatically.
- Configure the default states: every signal set to
deniedbefore the choice, updated afterwards. - Deploy through Tag Manager: Google's tags listen for the signals; the procedure is described in Consent Mode v2 with GA4 and GTM.
- Verify: Tag Manager's preview tool and the Google Ads diagnostic report show whether the signals are arriving; GA4 displays the share of modelled traffic; the effects on campaigns are covered in Consent Mode v2 and Google Ads.
- Add server-side measurement: server-side tracking and enhanced conversions recover part of the data the browser no longer passes on.
How GreenRed helps
Rather than juggling several tools, GreenRed's GA4 performance and traffic tracking brings these metrics together in a single dashboard, compares them over time and tells you which actions come first. You can try it free, with no card, from the Pricing.
Frequently asked questions
What is Consent Mode?
The mechanism through which a site passes the user's cookie choice to Google's tags. If they refuse, the tags switch to a degraded state and send anonymous signals with no identifier, which lets Google measure a volume and estimate the conversions lost.
Is Consent Mode v2 mandatory?
Google has required it since March 2024 for any site advertising to users in the European Economic Area. Without it, remarketing audiences stop being fed and some conversions are no longer attributed. It is not a legal obligation but a condition of using Google's services.
What is the difference between basic and advanced mode?
In basic mode, the tags only load after acceptance: no data if the visitor refuses, and therefore no modelling. In advanced mode, they load immediately and send cookieless signals, which enables conversion modelling and a more complete measurement.
How many conversions does modelling recover?
Between 30 and 70% of the lost conversions, depending on the site's volume. Modelling requires a minimum of traffic, in the order of 1,000 ad clicks and 100 conversions a month; below that it doesn't kick in, and the conversions from refusals stay invisible.