Privacy regulations require many websites to ask visitors for consent before using cookies for analytics and advertising. Google Consent Mode v2 is how Google tags learn about those choices and adapt. For marketers, it determines how much measurement data you keep when visitors decline cookies.
The four consent parameters
| Parameter | Controls |
|---|---|
| ad_storage | Storage of cookies related to advertising |
| analytics_storage | Storage of cookies related to analytics |
| ad_user_data | Whether user data can be sent to Google for advertising purposes |
| ad_personalization | Whether data can be used for personalised advertising such as remarketing |
Version 2 introduced ad_user_data and ad_personalization. Google's consent mode documentation explains each in detail.
Who needs Consent Mode v2?
If you have visitors from the European Economic Area and use Google Ads features such as remarketing, audience building or conversion measurement, Google requires valid consent signals. Many businesses outside Europe still receive European visitors. Other regions also have privacy laws with consent or opt-out requirements, so review your situation with legal advice.
Basic vs advanced Consent Mode
| Basic | Advanced | |
|---|---|---|
| Tags before consent | Not loaded | Loaded with consent defaults set to denied |
| Data when consent denied | None sent | Cookieless pings without identifiers |
| Modelling | Limited | Google can model conversions and behaviour for unconsented users |
| Privacy posture | Most conservative | Requires careful legal review |
Advanced mode preserves more measurement through modelling but sends limited, cookieless signals before consent. Some organisations prefer basic mode for a more conservative approach. Choose based on your legal advice and risk tolerance.
How to implement Google Consent Mode v2
- Choose a consent management platform (CMP) or banner that supports Consent Mode v2. Many certified CMPs integrate directly.
- Set default consent states before any Google tags fire, usually denied for users in regions requiring consent.
- Update consent when users make a choice, passing all four parameters.
- Configure tags in Google Tag Manager to respect consent, using built-in consent checks.
- Test with Tag Assistant: confirm defaults, updates and tag behaviour for accept and decline scenarios.
- Document your configuration and update your privacy policy.
Cookie banner analytics: what you lose and keep
When users decline analytics cookies:
- GA4 does not store cookies for those users.
- In advanced mode, cookieless pings allow Google to model some activity.
- Reports may show fewer users and conversions than reality, especially in regions with high decline rates.
Plan for this gap. Use CRM data and server-side lead records as the source of truth for leads, as described in our GA4 lead tracking guide.
GA4 consent and reporting
GA4 can apply behavioural modelling to fill gaps when enough data exists. Check whether modelling is active in your property's reporting identity settings. Explain to stakeholders that analytics numbers are estimates influenced by consent rates.
Cookieless tracking: what is realistic
There is no legitimate way to track individuals who declined consent as if they had accepted. Options that respect choices include:
- Aggregated, cookieless measurement through advanced Consent Mode.
- First-party data from forms and CRM (with appropriate notices).
- Server-side tagging, which improves control and data quality but does not remove consent requirements.
- Marketing mix modelling and incrementality testing at a channel level.
Consent Mode and Google Ads remarketing
Remarketing lists depend on ad_personalization consent. When users decline, they are not added to personalised audiences, so lists may shrink in regions with high decline rates. Plan audience strategies accordingly: rely more on contextual targeting, consented first-party customer lists and content that earns return visits organically.
Common mistakes
- Banners that do not actually block tags before consent.
- Missing ad_user_data and ad_personalization parameters.
- Default consent set to granted for all regions.
- No testing after website or tag changes.
- Privacy policy not updated.
Consent and conversion tracking
Ad platforms rely on conversion data to optimise. With consent gaps, consider enhanced conversions and offline conversion imports based on consented first-party data; see offline conversion tracking. Always confirm your approach with legal guidance.
If you need Consent Mode v2 implemented and tested across your site and tags, our conversion and analytics team can help.
Healthcare organisations face additional rules about tracking technologies; our healthcare digital marketing guide outlines the main considerations.
