Google Consent Mode: why Google Ads counts fewer customers than you actually get

Say an aluminium window company in Granollers advertises on Google Ads for “window replacement”. The ad leads to a page built only for the campaign, and the WhatsApp button on that page types its own opening line: “Hi, I'd like a quote for windows”. That way the owner knows which messages come from there. In October, 19 messages arrive with that line, and Google Ads reports 7 conversions. The owner is about to cut the budget because “the campaign isn't working”. But the campaign brought in 19 enquiries. Google only saw the people who accepted cookies; the rest turned them down or never touched the banner. And what Google gets to see is decided by Google Consent Mode.

What Google Consent Mode is

Google Consent Mode is the way to pass on to Google's tags what each visitor chose in your cookie banner. According to Google Ads Help on consent mode, it doesn't add a banner or any buttons of its own: it picks up the choice made in the banner you already have and changes how the Google Analytics and Google Ads tags behave.

Google receives separate permissions. Four of them matter to a business that advertises:

ad_storage. Whether advertising cookies can be stored, the ones that link the click on an ad to what the person does next on your website.

analytics_storage. Whether measurement cookies can be stored, the ones Google Analytics uses to count visits.

ad_user_data. Whether that person's data can be sent to Google for advertising purposes.

ad_personalization. Whether they can be shown personalised ads, such as remarketing ads that follow up people who have already visited your website.

Each permission ends up granted or denied. With everything granted, the tags work as usual. If any is denied, they stop storing cookies or using that data, depending on which one it is.

Why Google Ads counts fewer customers than you actually get

In Europe, a Google tag can only store its cookies if the person has said yes, and in Spain a lot of people say no. According to Eurostat's privacy figures, in 2025 72.9% of Spanish internet users aged 16 to 74 had refused, in the previous three months, to let their personal data be used for advertising. The EU average was 58.8%. On top of that, 32.4% had changed their browser settings to limit cookies.

That doesn't mean seven in ten visitors will reject your banner, but it does mean rejecting is an everyday habit. And there is a group no statistic covers: people who never touch the banner. They arrive on their phone, see the WhatsApp button and write. Legally, that isn't accepting: the cookie guide from the Spanish Data Protection Agency points out that simply doing nothing does not amount to consent. Until they press “Accept”, as far as Google Ads is concerned, that visitor did nothing.

The loss isn't proportional, though. Google explains that people who accept cookies usually convert two to five times more often than those who don't, and gives an example: an advertiser with a 50% consent rate saw measured conversions drop by 19%, not by half. In a business where almost everything comes in by phone and WhatsApp, like the window company, the gap can be wider, because many people write without going through the banner.

Basic or advanced Google Consent Mode

Google offers two ways to set it up, and they don't measure the same things.

With basic mode, Google's tags don't load until the person accepts. If they reject, nothing reaches Google, not even the fact that they rejected. To estimate what is missing, Google Ads then uses a general model rather than one built from your account's data.

With advanced mode, the tags load as soon as someone arrives, with permissions denied by default. Until the person accepts, they send Google cookieless signals: that a page was viewed, that a conversion happened, whether the visit came from an ad. Google says this lets the model fit your account and estimate better.

Before you switch on advanced Consent Mode

Google explains that these signals don't store cookies and that it doesn't use them to track individuals, build remarketing lists or create profiles. Even so, they leave the browser before the person has chosen, and the European cookie rule isn't only about cookies. The European Data Protection Board, in its Guidelines 2/2023 on the technical scope of that rule, includes for example pixels that make the browser send information to an advertising service. Before switching on advanced mode, check with whoever handles your data protection. We are not lawyers and this is not legal advice.

On the pages we send campaigns to, we use basic mode: until the person accepts, nothing from Google loads. For a small business, the advantage of advanced mode is small anyway, for the reason that follows.

Modelled conversions: the threshold few small businesses reach

Modelled conversions are the ones Google estimates, based on the people who did accept, to fill in what it couldn't see. They appear in the “Conversions” column, added to the measured ones. But Google doesn't calculate them for every account. Google Ads Help on consent mode modelling sets a threshold of 700 ad clicks over a seven-day period, per country and domain grouping, and only once that is met does a training period begin.

Google Analytics works in a similar way. To estimate the behaviour of people who reject cookies, the property must use advanced mode on every page, receive at least 1,000 events a day from visitors who rejected for seven days, and have at least 1,000 daily users who accepted on seven of the last 28 days. Even then, Google warns that it isn't guaranteed.

The window company in Granollers gets about 15 ad clicks a day, just over a hundred a week. That is a long way from 700, and its website doesn't get a thousand visits a day. Whatever Google Ads doesn't see, nobody is going to estimate: it simply goes uncounted. That is why, for a small account advertising in Europe, the number of conversions is nearly always a minimum, not the total.

Google Consent Mode v2: what Google requires in Europe

Google added two permissions to consent mode, ad_user_data and ad_personalization, in what its help pages call version 2. In the industry it is known as Consent Mode v2. At the same time, Google began enforcing its EU user consent policy more firmly: to keep using its measurement tags and personalised advertising with visitors from the European Economic Area, you have to ask them for permission and pass those signals on to Google. Since early March 2024, for example, if you don't, the Analytics audiences you use in Google Ads leave out European visitors.

Among other things, the policy requires valid consent for cookies and for using personal data in personalised ads, keeping a record of that consent and explaining clearly how to withdraw it. If you use a consent platform certified by Google, it updates to version 2 by itself; if your banner is your own, version 2 has to be built in. And for remarketing, the ad_personalization permission has to be granted: without it, that person doesn't go into your lists.

A cookie banner that complies without putting people off

Consent Mode won't fix a badly made banner. The Spanish Data Protection Agency's guide on the use of cookies (in Spanish), updated in May 2024, is clear on several points:

Rejecting has to sit at the same level as accepting. In the same layer, at the same time, with the same visibility and with a similar button. A “Reject” option hidden inside “Settings” doesn't count.

You can't nudge people into accepting. Not with a reject button in a colour that can't be read, and not with pre-ticked boxes. Carrying on browsing isn't consent either.

Withdrawing consent must be as easy as giving it. For example, with a link that is always within reach and reopens the settings panel.

Consent expires. The agency considers it good practice not to treat it as valid for more than 24 months.

Within those rules, the wording makes a big difference. One short sentence saying what you use cookies for (“to see which ads bring us customers”) is easier to follow than three paragraphs of legal text. And on mobile, the banner should be visible without covering what people came to do, such as the WhatsApp or call button. What the cookie policy and the other legal pages need to include is covered in the legal pages your website needs.

How to check that your Google Consent Mode works

There are four checks, and they don't take long:

1. With Tag Assistant. It is Google's free tool for checking tags. Connect your website and, in the “Consent” tab, you will see the starting state and how it changes when someone accepts or rejects. If the tab is empty, consent mode isn't set up.

2. In Google Ads. In the conversion diagnostics tab, Google Ads shows the consent mode status of your account.

3. In Google Analytics. In Admin, under “Data collection and modification”, you will find “Consent settings”. It shows how much of your traffic comes from the European Economic Area and whether you are receiving the advertising and measurement signals.

4. In your own browser. Open your website in a private window, press “Reject” and check in the developer tools, under cookies, that none of Google's appear: the ones starting with _ga or _gcl. Repeat after accepting and check that this time they do appear. If they show up before you press anything, the banner is just decoration: it asks, but measurement had already started.

How to count what Google doesn't see

If Google only sees part of it, you count the rest. Nothing complicated is needed:

One page per campaign. If the ad leads to a page that exists only for that ad, with a WhatsApp button that types its own opening line, every message with that line comes from there. Nothing is stored on anyone's phone: it is just the text of the message. Keep that page out of search results with a noindex tag and don't link to it from your menu, so it doesn't get visits from elsewhere.

The usual question. “How did you hear about us?”, in the first message or the first call, and written down. How to do it without getting tangled up is explained in how to find out where your customers come from.

A monthly comparison. Put the campaign's real enquiries next to the Google Ads conversions. If, month after month, Google sees roughly the same share, say four in ten, that share helps you read the account.

That way each number has its job. Google Ads conversions are for comparing within the account: which keyword brings more enquiries, at what time, with which ad. To know whether the campaign pays off, go by your own count. And bear in mind that automated bidding strategies that chase conversions only learn from the ones Google sees: with few of them, they learn slowly. Other ways a budget leaks are in Google Ads spends and doesn't sell, and what to look at in your visits is in web analytics.

How we set up Google Consent Mode

On the pages we send campaigns to, the banner is our own and runs in basic mode. Until the person presses “Accept”, nothing from Google loads, no cookies and no requests. On accepting, only measurement is switched on: the ad click is stored and the conversion is counted, but remarketing stays off. “Reject” sits next to “Accept” and is the same size.

There is one detail that saves conversions. If someone arrives from an ad and doesn't decide on the first page, the click identifier travels in the website's internal links without being stored on the device; if they accept on the second page, the conversion can still be linked to the ad. Google has a similar option in consent mode, which passes that information through the URLs when permission is denied.

The conversions we count are the ones that bring in customers: a tap on the WhatsApp button, a form sent and a tap on the phone number, one per ad click. Izan sets up the measurement and checks it with Tag Assistant and in the browser, Ivan codes the banner so it doesn't slow the website down, and Jordi writes the copy so it is clear at first read.

What it costs to have it set up properly

If we build your website, measurement is included: Your Landing, at €100 a month, and Your Website, at €200 a month, come with measurement in place. Google Ads and Meta Ads management, with setting up, monitoring and adjusting the campaigns, is part of the presence plans at €750 and €1,500 a month. All prices exclude VAT, with no minimum term and no setup fee, as shown on our pricing page.

Ad spend is separate: it goes straight to Google, on your card and in your name, and we add no margin to it. If you already have a website and only want the banner and the measurement reviewed, we give you a fixed price for whatever needs doing. What we do on each channel is on our digital marketing page.

Where to start

Run the browser test today: private window, “Reject”, and see whether Google cookies appear. If they do, the problem is a legal one before it is a measurement one. If they don't, but your conversions don't match the messages you get, now you know why.

If you want us to look at it with you, message us on WhatsApp with your website address and the campaigns you are running. In a first, no-obligation chat, we'll tell you what we would look at first. You can also write to us through the contact form.