Google Consent Mode v2: understanding the signals and installing it properly

Since March 2024, every European site that uses Google Ads or Google Analytics must pass its visitors' consent status to Google through Consent Mode v2. Without these signals, no more remarketing, no more custom audiences, and degraded conversion measurement. Here is how this mechanism works and how to install it correctly.

Why Consent Mode has become unavoidable

Consent Mode is the API through which a site tells Google services whether the visitor has consented, or not, to the setting of cookies and the use of their data. Google tags then adapt their behavior: with consent, they work normally; without consent, they stop setting cookies.

Version 2 was made mandatory by Google in March 2024 for the European Economic Area, in the wake of the Digital Markets Act. Concretely: without valid Consent Mode v2 signals, Google Ads no longer accepts European audience data, and remarketing and ad personalization stop working for your European visitors.

The four signals

Consent Mode relies on flags set to granted or denied. The first two existed from v1, and v2 adds two:

• ad_storage: setting of advertising cookies;
• analytics_storage: setting of audience measurement cookies;
• ad_user_data (v2): sending of user data to Google for advertising purposes;
• ad_personalization (v2): use of data for ad personalization (remarketing).

The lifecycle is simple: a default state is declared before any Google tag loads (gtag('consent', 'default', …)), then updated when the visitor makes their choice in the banner (gtag('consent', 'update', …)).

Basic or advanced mode

Two implementations are possible. In basic mode, Google tags do not load at all until consent is given: nothing is sent, but Google receives no data from visitors who refuse. In advanced mode, tags load from the first page but, without consent, are limited to technical signals with no cookie or identifier; Google uses them to statistically model the missing conversions.

Advanced mode offers better measurement, at the cost of network exchanges with Google even in case of refusal. This is a trade-off to make knowingly, ideally documented in your privacy policy.

The three classic mistakes

• The default declared too late. The consent default block must run before any Google tag, at the top of the page. If declared after, the first hits go out with cookies even though the visitor has accepted nothing.
• The update never sent. The banner collects the choice but does not pass it to Google: the signals stay at denied and your campaigns lose their data even for consenting visitors.
• The v2 signals forgotten. A v1 integration that sets neither ad_user_data nor ad_personalization is considered incomplete by Google Ads.

The simplest approach: let the CMP handle it

A consent management platform (CMP) that natively integrates Consent Mode v2 declares the default at the right time, sends the update as soon as the visitor chooses, covers the four signals and keeps the proof of consent. All that remains is to place your Google tags as usual.

This is how Consenteer works, including on this very site: our own Google signals are driven by our own banner. The installation comes down to one line of script.