Consent Mode v2: What It Is and How to Set It Up

What Is Google Consent Mode v2

Google Consent Mode v2 is Google's protocol that adjusts the behavior of measurement tags (Google Analytics 4, Google Ads, Floodlight) based on the consent the user has granted or denied through the cookie banner.

The original version already allowed sending cookieless pings when the user rejected consent. Version 2 introduces two additional parameters that change the rules:

ad_user_data: controls whether user data can be sent to Google for advertising purposes.
ad_personalization: controls whether personalized advertising is allowed (remarketing, similar audiences).

Since March 2024, Google requires Consent Mode v2 for any advertiser wanting to use audiences and conversion measurement in the European Economic Area (EEA) and the UK.

Why It Matters for CRO and Analytics

Without Consent Mode v2 properly implemented, you lose data in two ways:

Conversion Data Loss

If a user rejects cookies and you don't have Consent Mode, the Google Ads tag simply doesn't fire. That conversion disappears completely from your reports. With Consent Mode active, Google uses modeling to estimate conversions from users who didn't give consent, recovering between 30% and 70% of lost data depending on the industry.

Audience Data Loss

Without the ad_user_data parameter configured, you can't feed remarketing audiences or create lookalikes in Google Ads for EEA users. This directly impacts your campaign performance and, therefore, your cost per acquisition.

Basic vs. Advanced Mode

Consent Mode v2 can be implemented at two levels:

Basic Mode

Google tags only load when the user accepts. If they decline, no data is sent. It's the most conservative option and the simplest to implement, but you lose all information from users who reject.

Advanced Mode

Tags always load, but their behavior changes based on consent:

With consent: normal operation with cookies.
Without consent: cookieless pings are sent without personal identifiers. Google uses these anonymized pings to feed its conversion models.

Advanced mode is recommended for most businesses because it maximizes data recovery without compromising privacy.

How to Implement Consent Mode v2

Prerequisites

A compatible consent management platform (CMP): Cookiebot, OneTrust, Didomi, Usercentrics, or similar.
Google Tag Manager (recommended) or gtag.js.
GA4 and/or Google Ads configured.

Implementation with GTM

Set default values: in the GTM configuration, establish the initial consent values before the banner loads:

gtag('consent', 'default', {
  'analytics_storage': 'denied',
  'ad_storage': 'denied',
  'ad_user_data': 'denied',
  'ad_personalization': 'denied',
  'wait_for_update': 500
});

Connect your CMP: configure your consent platform to update the states when the user interacts with the banner.
Verify with Tag Assistant: use Google Tag Assistant to confirm that consent states are sent correctly with each hit.

Impact on Data: What to Expect

After implementing Consent Mode v2 in advanced mode, these are the typical changes in data:

Metric	Without Consent Mode	With Consent Mode v2
Tracked conversions	Only consenting users	All (measured + modeled)
GA4 sessions	Only with consent	Anonymized pings + full sessions
Remarketing audiences	No EEA data	Data with explicit consent
Attribution accuracy	Low (incomplete data)	Improved with modeling

In markets with high cookie rejection rates (Germany, France), the difference can be 40-60% more reported conversions.

Common Implementation Mistakes

Not Setting wait_for_update

If you don't set a wait time for the CMP to load, tags may fire with the default denied values before the user has a chance to accept. This generates unnecessarily incomplete data.

Forgetting ad_user_data and ad_personalization

Many implementations only update analytics_storage and ad_storage but forget the two new v2 parameters. Without them, you don't meet Google's requirements for the EEA and lose advertising functionality.

Not Testing by Market

Cookie acceptance rates vary enormously by country. Test the implementation in each market where you operate and adjust the banner design to maximize acceptance without being intrusive.

Consent Mode and Server-Side Tagging

If you use server-side tagging with GTM, Consent Mode v2 works similarly: consent states are sent to the server container, which decides what data to process and forward to endpoints (GA4, Google Ads, Meta CAPI).

The advantage of server-side is that you can apply additional consent logic before sending data to third parties, giving you more control over what information leaves your infrastructure.

At Boost, we implement Consent Mode v2 as part of our analytics configuration so our clients measure their conversions correctly without compromising user privacy. If you need help with your implementation, talk to our CRO team or analyze your site for free with Scan&Boost.

Adrià Vidal — Boost