In Europe you cannot measure anybody without their permission. That collides head-on with the previous lesson: the Google tag needs cookies to link click and conversion. Google resolved the tension with Consent Mode, and since 2024 it has been compulsory in order to use measurement and audience features in the European Economic Area. This lesson explains what it is, how you set it up and what happens to the data of the people who say no.
The framework: GDPR and ePrivacy
- Advertising and measurement cookies require prior, informed and freely given consent: a banner that lets people accept and reject with the same ease. Data protection authorities fine banners with «accept» in large type and «reject» tucked away.
- Until the person decides, those cookies cannot be set.
- Consent is managed with a CMP (consent management platform): Cookiebot, Usercentrics, OneTrust, Complianz, iubenda and dozens more. Google requires the CMP to be certified for its Consent Mode.
What Consent Mode does
The CMP tells Google's tags the status of consent (ad_storage,
analytics_storage, ad_user_data, ad_personalization: granted or
denied). The tags adapt:
| Version | If the person rejects... | What you get |
|---|---|---|
| Basic | Google's tags do not load until there is consent | You comply; Google can only model with a generic model |
| Advanced | The tags load but without cookies: they send anonymous «pings» (with no identification of the person) | You comply; Google models your lost conversions using your own data |
Advanced is the one Google recommends and the one that recovers the most data. It is lawful if the CMP is properly configured: pings without consent contain no identifiers. Check with your legal adviser, but it is the industry standard in 2026.
Modelling: recovering what you can't see
In advanced mode, Google compares the behaviour of the people who did accept with the anonymous pings from those who didn't, and estimates how many conversions happened among the ones that cannot be observed. Those modelled conversions are added to the conversions column (with a note in the report) and Smart Bidding uses them. Without modelling, on a site with a 40% rejection rate, your bids would be learning from half of reality.
Conditions for modelling to work: advanced mode properly implemented, enough volume (as a guide, hundreds of clicks with and without consent in each group) and tags on every page.
How it is implemented (no code)
- Choose a CMP certified by Google and install it (almost all of them have a plugin for WordPress/Shopify, or are added from Tag Manager).
- Switch on the integration with Google Consent Mode (v2) in the CMP: it is a checkbox in almost every one.
- If you use Tag Manager: advanced mode is usually the default behaviour of the CMP's template; check that Google's tags do not have triggers blocking them until consent (that would turn them into basic mode).
- Verify (next section).
Verifying
- Tag Assistant: on every page it shows the consent status the tags receive; when you reject in the banner they must go to «denied» and keep sending pings (advanced mode).
- Google Ads → Goals → Conversions → Diagnostics: the Consent Mode section shows whether the tags are communicating it and whether there are problems.
- Statuses to watch out for: «Consent Mode not detected» (there is no integration) or «consent denied 100% of the time» (the CMP is always sending «denied»: a configuration error, and you will measure nothing).
Common mistakes
- A banner with only «Accept»: unlawful and, on top of that, Google may restrict features.
- A CMP installed but with the Google integration not switched on: the tags never hear about consent → either they measure everybody (unlawful) or nobody (if they are blocked by default).
- Duplicated tags (one going through the CMP and another not).
- Changing CMP and not verifying again.
💡 Ninja trick: the existence and quality of a CMP is also a legitimacy signal for a website: serious sites have one; site farms built to collect impressions almost never do. Our Ninja Shield uses the presence of a CMP (alongside trust badges, a company registration number, social profiles, domain age...) as one of its trust signals when deciding which Display sites deserve your money and which do not.
What you should remember
- In Europe, tracking requires consent managed by a certified CMP, with rejecting as easy as accepting.
- Consent Mode v2 is compulsory: in advanced mode, Google models the conversions of people who reject and Smart Bidding uses them.
- Implementing = CMP + integration switched on + verifying in Tag Assistant and in the conversion diagnostics.