Consent Mode v2 without nuking your data
Set up Consent Mode v2 the right way: GDPR compliance AND conversions intact.
Draft — reviewed and completed by Yoann before publishing.
Consent Mode v2 has become unavoidable if you want to keep measuring and stay compliant. But misconfigured, it can cost you a huge share of your data. Here’s how to set it up without bleeding your measurement.
Why Consent Mode
With strict GDPR enforcement and Google’s requirements (notably for remarketing and audiences), “just block the tags until there’s consent” no longer cuts it. Consent Mode lets Google model the conversions lost when a user declines — provided everything is wired correctly.
Basic vs Advanced
- Basic: tags don’t load until consent is granted. No modelling, or very limited.
- Advanced: tags load and send anonymous, cookieless pings on refusal. Google can then model the missing conversions. It’s the mode that preserves the most data — but it demands a rigorous setup.
Conversion modelling
In advanced mode, Google uses the anonymous signals + its models to estimate conversions from non-consenting users. In practice, on well-configured accounts, you recover a significant share of the “lost” conversions. But modelling needs volume and clean wiring to kick in.
Common mistakes
- Firing tags before Consent Mode init → consent states ignored.
- Forgetting to set the default values before the CMP loads.
- Mixing CMP and tags without
wait_for_update. - Not testing both paths (accept / decline) in preview.
The recommended setup
- A certified CMP (abconsent, for example) that pushes Consent Mode signals.
gtag('consent', 'default', …)loaded first, before any other tag.- Advanced mode if volume allows.
- GTM Preview check: both consent scenarios, and correct
consent state. - Confirm in GA4 / Ads that modelling activates.
Done right, Consent Mode v2 isn’t a loss: it’s the best trade-off between compliance and keeping your data.