If you use Google Ads or Google Analytics and have customers from Europe, the following information is absolutely crucial for you. Since 21 July 2025, companies have been reporting significant problems with conversion measurement. Without a correctly set up Google Consent Mode v2 you are losing the accurate conversion data you need to evaluate the success of your campaigns. Let’s look at what changes have arrived and how to deal with them.
Summary for Those Who Don’t Have Time to Read the Whole Article
- Google Consent Mode v2 has been mandatory since March 2024 for everyone who targets users from the EU and the UK.
- Since 21 July 2025, outages in conversion measurement have started to appear for those who do not have it implemented.
- Without the correct setup Google blocks your conversions (sales, form submissions, etc.) and it has a negative impact on remarketing.
- There are two implementation variants, basic and advanced (advanced preserves more data).
- Implementation is possible via gtag.js or Google Tag Manager (GTM is easier to manage).
What Is Google Consent Mode v2?
Your website needs to communicate with Google about what the user has and hasn’t allowed it to track. Consent Mode v2 is the communication bridge. When a user clicks on the cookie banner and allows or denies something, this tool translates it into a language Google understands.
How Does It Work in Practice?
When someone comes to your website, a cookie banner pops up asking for consent. Depending on what the user agrees to, Consent Mode v2 sends Google the information in the form of four parameters:
- analytics_storage – permission to store cookies for analytics.
- ad_storage – permission to store cookies for advertising.
- ad_user_data – consent to sending user data (e.g. the email you enter when making a purchase)
- ad_personalization – consent to using data for personalised ads.
What Is the Difference Between the Cookie Banner and Consent Mode?
The cookie banner is what the user sees – a window with “Accept all” or “Reject” buttons. It is a visual element on your website.
Consent Mode v2 is a technical solution in the background that ensures the user’s decision is actually respected when data is sent to Google Analytics and Google Ads. It communicates the user’s consent or refusal to Google tags and SDKs (for mobile apps). The tags of other systems, such as Facebook Ads, TikTok, etc., can be tied to Consent Mode v2.
A Critical Change Since 21 July 2025
The most serious news is that since 21 July 2025 advertisers have been reporting significant outages in conversion measurement. What does that mean in practice?
- You don’t see the real number of orders that your Google Ads campaigns brought.
- Some conversions are not recorded. It is not a complete outage, but significant gaps in the data.
- Data about important actions on your website is missing.
Google has not issued an official statement about “switching off” conversion measurement as of this date, but the observed behaviour clearly shows a restriction of data collection.
Why Is This Absolutely Crucial Information for Your Business?
A badly set up Consent Mode v2 has a direct impact on your ability to manage and optimise advertising campaigns. The following problems show up immediately and their impact worsens over time.
- Running campaigns blind – Without accurate conversion measurement you are flying blind. You cannot know which campaigns, keywords or creatives work and bring real results.
- Poor optimisation – The Google Ads algorithms need quality conversion data to optimise bids and ad delivery effectively. If this data is missing, your campaigns will be less effective and you will probably see a significant drop in performance.
- Limited conversion modelling – Consent Mode v2 (especially in the advanced variant) allows Google to use so-called conversion modelling. This means that even if the user does not give full consent to cookies, Google can estimate the missing conversions based on aggregated and anonymised data. Without a correct implementation of Consent Mode v2, this valuable feature is limited or switched off entirely.
- Risk of a fine from the Czech Office for Personal Data Protection (ÚOOÚ) – The Czech Office for Personal Data Protection is actively investigating compliance with the rules on cookies and obtaining consent. If you do not have your cookie banner set up correctly or you obtain consent in an inappropriate way, you risk a fine of up to 20 million euros or up to 4% of total annual worldwide turnover for the previous financial year – whichever is higher. The ÚOOÚ is currently registering more than 80 complaints about the use of the “consent or pay” principle and is actively conducting proceedings with several entities in the Czech Republic.
The Evolution from Version 1.0 to Version 2.0
Consent Mode is not a new thing; it has existed for several years and has gradually evolved. The original version was simpler and dealt with basic questions about cookies. The current version 2.0 is much more complex and responds to tightening European legislation.
The Original Consent Mode 1.0
The first version worked with only two parameters: ad_storage and analytics_storage. It dealt with the basic question: can Google store cookies, or not?
The status code was transmitted using the gsc parameter, which took different values depending on what the user allowed.
The New Version 2.0
Since March 2024 two new parameters have been added that give users more control, namely the already mentioned ad_user_data and ad_personalization.
The status code in GCM 2.0 is transmitted using the gcd parameter with a more complex encoding of all four parameters.
Why this change? Google is trying to comply with stricter European personal data protection laws, specifically the Digital Markets Act within the European Economic Area.
Two Implementation Variants (Basic and Advanced)
You can implement Consent Mode v2 in two ways. Each variant has its advantages and disadvantages, which affect the amount of data you will have available for optimising campaigns. Choosing the right variant depends on your priorities: whether you prefer maximum privacy protection, or need as much data as possible for effective marketing.
Basic
If the user has not given consent, all Google tags are blocked and no data is sent to Google servers. After the user interacts with the cookie banner (CMP), consents are updated and, in the case of consent, sending data using Google tags is allowed.
In the case of refusal or no consent given, no anonymised (cookieless) pings with data are sent to Google servers in this mode.
In this mode less data is sent to the advertising systems than in the advanced variant. Conversion modelling is therefore less accurate. It is based only on data from users who actually gave consent to sending.
Advanced
The advanced method makes it possible to run the measurement codes (tags) even before the user has had time to react to the cookie notice. The system, however, keeps watch over what exactly may be sent. If the user has not yet agreed to storing cookies, none are stored or sent. At the same time, ad personalisation is switched off automatically until they give permission, and only basic, anonymous data is sent.
When the user has rejected cookies, Google still collects anonymised data (so-called pings) containing:
- The country the user comes from (from the IP address)
- The time of the visit (timestamp)
- The browser and device type (from the user agent)
- The address of the visited page and its referrer
- A random number instead of a user identifier
- Information about the CMP (Consent Management Platform) product
- Information about the consent state
Google Analytics and Floodlight tags automatically send, via pings, information about both the current and the changed consent state.
The user’s interaction with the cookie banner then triggers a consent update, and based on it the Google tags (markers) belonging to the categories the user has consented to are run.
Google prefers certified cookie banner providers – CMPs (Consent Management Platforms), a list of which you can find here, especially for participants in the AdSense programme. Google Ads users can have a cookie banner under their own control, but they still have to implement Consent Mode v2.
Implementation Methods
You can implement Google Consent Mode v2 in two basic ways.
Gtag.js: Implementation in Code
This method requires direct intervention in the website’s code, which means close cooperation with a webmaster or developer. All measurement tags (Google Analytics, Google Ads, remarketing, etc.) must be modified in the code so that they react correctly to the user’s consent state. It is a more demanding procedure, because every change requires editing the code on all pages of the website or in the whole application.
Adjusting Consents Within the Google Tag Manager Platform
Why adjust consents in Google Tag Manager? You don’t have to rewrite anything in the code on every page. You make all changes simply in the GTM container interface, or in the settings of your cookie banner (CMP). When something needs to be adjusted, you change it in one place and it is reflected across the whole website. There is no need to ask programmers for code changes with every modification.
How Consent Settings Work
Regardless of the chosen implementation method, consent settings always work in two phases. The first setting defines the default state of consents (default), which is used when the page first loads. The second setting then ensures that these consents are updated (update) after the user reacts to the cookie banner and selects their preferences.
Frequently Asked Questions
Since when has GCM v2 been mandatory?
The obligation has applied since March 2024 to all websites and apps that target users from the European Union and the United Kingdom.
Which parameters does GCM v2 track?
The new version works with four parameters. analytics_storage concerns consent to analytics, ad_storage determines the possibility of storing advertising cookies, ad_user_data relates to sending user data and ad_personalization allows the use of data for personalised ads.
What has changed compared with version 1.0?
Version 2.0 added two new parameters and a more complex encoding of information in order to comply with tightened European legislation on personal data protection.
What are the risks of a bad GCM v2 setup?
A badly set up system leads to inaccurate conversion data, weaker optimisation of advertising campaigns and worse results in both targeting and ad performance.
How do I implement GCM v2?
Implementation can be done by editing the code on all pages via gtag.js or by using Google Tag Manager. The second variant is easier to manage and does not require changes to the code with every modification.
Sources
Dekker, A. 2025. Google Ads freelancer Rotterdam – Cookiebot ad & ads [LinkedIn update], 6 August 2025. Available at: https://www.linkedin.com/posts/adriaan-dekker-google-ads-freelancer-rotterdam_cookiebot-ad-ads-activity-7355624024900550657-NLRG/
Slížek, D. 2025. The ÚOOÚ is handling more than 80 complaints about “consent or pay”, proceedings so far only against Seznam. Lupa.cz, 12 May 2025. Available at: https://www.lupa.cz/aktuality/uoou-resi-pres-80-stiznosti-na-souhlas-nebo-zaplat-rizeni-stale-vede-jen-se-seznamem/