TL;DR
Consent Mode v2 changes how Google Ads measures and optimises your campaigns in Europe. When a user refuses cookies, Google no longer receives a direct conversion signal, but uses modelled conversions to fill the gaps. Switching from basic mode to advanced mode can change the volume of conversions visible in your Google Ads account by 15 to 30%. Understanding this mechanism is essential to manage your advertising budgets without losing visibility.
Why Consent Mode v2 is a game changer for Google Ads
Since March 2024, Consent Mode v2 has been mandatory for advertisers targeting users in the European Economic Area (EEA) and the United Kingdom. Without this integration, Google Ads can no longer measure conversions, build remarketing audiences or optimise automated bidding for European traffic.
The practical problem: if your CMP blocks Google cookies before consent (as the GDPR requires), your Google Ads tags no longer fire for users who refuse. Consent Mode v2 is Google's technical answer to this signal loss.
How does Consent Mode v2 work with Google Ads?
Consent Mode v2 sends Google the consent status of each visitor via two main parameters: ad_storage (advertising cookies) and analytics_storage (analytics cookies). When the user refuses, these parameters switch to "denied" and Google Ads adapts its behaviour.
What happens when ad_storage is denied
When ad_storage is "denied", Google Ads no longer sets the _gcl cookie (gclid, gclsrc). Classic conversion tracking (via cookie) is disabled. Google then uses conversion modelling (an algorithm that estimates missing conversions based on the behaviour of users who accepted cookies). This mechanism requires a minimum volume of around 50 conversions per day to work properly.
Basic mode vs advanced mode: the difference for your campaigns
In basic mode, no Google tag fires before consent. Google has no data on visitors who refuse, so no modelling is possible. In advanced mode, tags fire without cookies (anonymous pings), which gives Google enough signal to model the missing conversions.
For Google Ads campaigns, this distinction is decisive. Advanced mode recovers on average 50 to 70% of the conversions that would be invisible in basic mode, according to benchmarks shared by Google. This directly affects bid optimisation (Smart Bidding) and the quality of your audiences.
What is the actual impact on your Google Ads metrics?
The impact of Consent Mode v2 on your Google Ads campaigns depends on your consent rate, your volume of European traffic and the mode you choose (basic or advanced). These are the most affected metrics.
Conversions and ROAS
With a consent rate of 70%, around 30% of your actual conversions are not measured directly. In advanced mode, Google models part of these missing conversions and shows them in your report. In basic mode, these 30% disappear completely from your reports. Your reported ROAS will therefore be lower than it really is, which can lead to wrong budget decisions.
Audiences and remarketing
Google Ads remarketing lists are only populated with users who accepted ad_storage. If your consent rate is 70%, your remarketing audiences only cover 70% of your actual traffic. In advanced mode, audiences are also enriched by modelled signals, but coverage remains lower than in a scenario without consent constraints.
Smart Bidding and automated bidding
Automated bidding strategies (tCPA, tROAS, Maximise Conversions) depend directly on the volume and quality of conversion signals. Fewer visible conversions means less data for the algorithm, and therefore potentially less accurate bids. Advanced mode mitigates this problem by providing modelled conversions that Smart Bidding includes in its calculations.
Comparison: basic mode vs advanced mode for Google Ads
Advanced mode offers much better visibility of conversions and audiences, which makes it the recommended choice for Google Ads advertisers in Europe. Basic mode suits sites that prefer not to fire any tag before consent, at the cost of significant data loss.
Common mistakes with Consent Mode v2 and Google Ads
Not checking that Consent Mode is properly integrated with your CMP. Many advertisers assume their CMP automatically sends Consent Mode signals to Google. That is not always the case. Check in Google Tag Manager that the ad_storage and analytics_storage parameters actually change according to the user's choice.
Comparing before/after performance without accounting for seasonality. The switch to Consent Mode v2 often coincides with other changes (budget, seasonality, new campaigns). Isolate the impact by comparing modelled vs direct conversions over the same period.
Staying in basic mode by default without measuring the impact. Some CMPs configure Consent Mode in basic mode by default. If you actively use Google Ads, the difference between basic and advanced can mean 20 to 40% fewer conversions in your reports.
Ignoring the minimum conversion threshold for modelling. Conversion modelling only works if you have sufficient volume (around 50 conversions/day). Low-volume accounts will not benefit from modelling, even in advanced mode.
Forgetting to configure ad_user_data and ad_personalization. Consent Mode v2 adds two new parameters: ad_user_data and ad_personalization. Without them, Google cannot use first-party data for targeting or for Customer Match audiences.
Checklist: Consent Mode v2 and Google Ads
- Check that your CMP sends all 4 Consent Mode parameters (ad_storage, analytics_storage, ad_user_data, ad_personalization)
- Choose between basic mode and advanced mode based on your compliance strategy and your data needs
- Test the integration in GTM using preview mode: simulate a refusal and check the consent states
- Monitor the volume of modelled conversions in Google Ads ("Conversions" column > segment by type)
- Check that your remarketing audiences keep filling up normally
- Compare your ROAS before and after activation over a stable period
- Make sure Enhanced Conversions are enabled to maximise signal quality
- Monitor your consent rate via your CMP and adjust the banner design if necessary
- Document your Consent Mode configuration in your GDPR record of processing activities
Conclusion
Consent Mode v2 is not an obstacle to advertising performance, but it changes the rules of the game. Advertisers who understand how it works and choose the right mode (basic or advanced) for their strategy can keep solid visibility of their conversions while remaining GDPR compliant.
The starting point: check your current integration and measure the gap between your direct and modelled conversions. Scan your site for free with FlowConsent to check that your Consent Mode configuration is working.