When a visitor rejects analytics and advertising cookies on your banner, the intuitive reaction is to think Google Analytics and Google Ads stop receiving any information about that visit at all. In practice, there is an intermediate system, called Consent Mode, that allows some aggregated, non-identifying information to still be received, instead of losing all visibility at once. Understanding how it works helps correctly interpret why your analytics data does not exactly match your website's real visits.
What the difference is between data with consent and without it
With full consent, Google receives information normally, linked to that specific visitor's identifier. Without consent, on the other hand, it only receives aggregated, anonymous signals (for example, "a visit happened" with no link to any particular person), which Google uses to estimate, through statistical modelling, the behaviour of the group of users who rejected, without being able to identify them individually.
Why it became mandatory, not just recommended
For businesses in the European Economic Area using Google Ads or Analytics, having Consent Mode correctly configured is no longer optional: it is a technical requirement for certain measurement and remarketing features to keep working legally, while still respecting the user's actual decision about cookies.
How to know if your website already has it configured correctly
The most reliable way to check is using the browser's developer tools to see whether, after rejecting cookies on the banner, the consent signals update correctly in the requests going out to Google, instead of still sending exactly the same data as if everything had been accepted.
The effect it has on your usual reports
With Consent Mode active, it is normal to see a difference between your website's real number of sessions (measured, for example, by the server) and the number of sessions shown in Analytics, precisely because a portion of the visitors who rejected cookies are being statistically modelled, not counted one by one as before.
Frequently asked questions
Do I need to install something new to have Consent Mode active?
It depends on your consent management platform (CMP): many already integrate it automatically with Google Tag Manager, but it is worth verifying the installed version is the updated one (v2), not an old, already deprecated version.
Does Consent Mode replace the cookie banner?
No, it is complementary: the banner still collects the user's actual decision; Consent Mode is the technical mechanism that communicates that decision to Google and adjusts what data gets sent accordingly.
Does this also affect Meta (Facebook and Instagram) advertising?
Meta has its own equivalent system, the Conversions API, with similar but not identical logic; it is worth reviewing each advertising platform's configuration separately, not assuming that setting up one automatically covers the others.