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Google Consent Mode: what to actually do

Since March 2024, Google has required advertisers using Google Ads and its advertising features on visitors from the European Economic Area and the UK to pass consent choices to it via Consent Mode v2. That’s a requirement set by Google for its own products, separate from the legal obligation to collect consent, which comes from GDPR and falls under the CNIL’s remit in France.

Describe my issue Send a message

What I see most often

  • A Google Ads notice flagging missing consent signals for European Economic Area visitors
  • A custom consent banner that collects the visitor’s choice correctly but sends nothing to Google
  • Confusion between "collecting consent" (a GDPR obligation overseen by the CNIL) and "passing consent to Google" (a Google Ads-specific requirement)
  • Remarketing or conversion modelling that seems to have weakened since a consent banner went live
  • A third-party CMP to choose from without knowing whether it handles consent mode automatically

How the mechanism works

Consent Mode v2 relies on four signals sent to the Google tag: analytics_storage for analytics storage and ad_storage for advertising storage, both already in v1, to which v2 adds ad_user_data (permission to send user data to Google for advertising purposes) and ad_personalization (permission to personalise advertising, remarketing included). Those last two are what make it v2: an implementation that only sends ad_storage and analytics_storage is still on v1, and that is the most common case I find on custom banners.

All four are sent a first time by default, before the visitor has responded to the banner, then updated once they make a choice.

There are two ways to implement this. A Consent Management Platform (CMP) certified by Google integrates it automatically: it sends the right signals at the right time with no extra code to write. A custom-built banner has to implement these calls by hand via the gtag('consent', ...) function, once for the default state, once more for the update when the visitor decides.

What I check and set up

  1. Does this apply to me?

    I check whether the site uses Google Ads or Google advertising features (remarketing, Customer Match, conversion modelling) on visitors located in the EEA or the UK: that’s the exact scope of Google’s requirement.

  2. State of the existing banner

    I check whether the consent banner in place is a Google-certified CMP (automatic implementation) or a custom solution (manual implementation to verify or build).

  3. Default state before the decision

    I make sure a default consent state (usually denied) is sent before the visitor has even responded to the banner, a condition the mechanism needs to work correctly.

  4. Update on decision

    I check that the visitor’s actual choice (accepted or refused, by category) triggers an update call sent to Google the moment they click.

  5. Checking the signals

    Using Google Tag Manager’s preview mode or a debugging extension, I confirm consent signals appear correctly attached to the relevant Google Ads and GA4 tags.

consent-mode.js
gtag('consent', 'default', {
  'ad_storage': 'denied',
  'ad_user_data': 'denied',
  'ad_personalization': 'denied',
  'analytics_storage': 'denied'
});

// après la décision du visiteur sur la bannière
gtag('consent', 'update', {
  'ad_storage': 'granted',
  'ad_user_data': 'granted',
  'ad_personalization': 'granted',
  'analytics_storage': 'granted'
});

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Frequently asked questions

Is Consent Mode a French legal obligation?
No. It’s a requirement set by Google to keep using Google Ads and its advertising features on European visitors. The legal obligation to collect consent comes from GDPR and the ePrivacy directive, and is overseen by the CNIL, independently of what Google asks for.
What happens if I don’t pass any consent signal to Google?
Ad personalisation, remarketing and conversion modelling features are disabled or degraded on Google Ads for the visitors concerned. That’s not the same as audience measurement itself stopping.
Does my CMP handle Consent Mode automatically?
It depends on whether it’s Google-certified. A certified CMP implements it automatically. A custom-built banner has to call gtag('consent', ...) by hand, which needs a specific technical check.
Does Consent Mode replace collecting consent itself?
No. It assumes consent has already been collected from the visitor under the rules that apply in France; it simply passes that choice on to Google for its own advertising products.
Do I need Consent Mode if I don’t use Google Ads?
Google’s requirement targets advertisers using Google Ads and its advertising features. If a site only uses audience measurement without those features, this specific requirement doesn’t apply the same way, though the legal obligation to collect consent still needs handling separately.

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