Consent mode v2 for UK sites, in plain English.

What consent mode is

Your cookie banner collects a visitor's choice. Consent mode is the set of signals that passes that choice to Google's tags: Google Analytics, Google Ads and Floodlight. The tags then change how they behave.

Consent mode is not a cookie banner, and it does not make you compliant on its own. You still need a banner that asks properly, and you still need tags from Meta, LinkedIn, TikTok and others to respect the same choice. Consent mode only covers Google's side.

The four signals

Version 2 uses four signals, each either granted or denied. analytics_storage controls whether analytics cookies, such as GA4's visitor ID, can be set. ad_storage controls whether advertising cookies can be set.

The two newer signals are ad_user_data, which controls whether data about the visitor can be sent to Google for advertising, and ad_personalization, which controls whether that data can be used for personalised advertising such as remarketing.

The newer signals arrived because of EU rules on large platforms. Google requires them for advertisers using its ad features with users in the European Economic Area and the UK, so UK sites running Google Ads should have them set.

How it works on a page

Before any Google tag loads, the page sets a default for each signal. For UK visitors, that default should be denied for anything that needs consent. The visitor then makes a choice in the banner, the page updates each signal to granted or denied to match, and Google's tags read the signals and either behave normally or hold back.

The most common fault we find is order. If a Google tag loads before the default is set, it may set cookies before the visitor has chosen. Check this in your browser's developer tools on a fresh visit.

Basic and advanced mode

There are two ways to set consent mode up, and they affect your data differently.

In basic mode, Google's tags do not load at all until the visitor consents. If they decline, nothing is sent to Google. Your reports show less data, but only from people who agreed, and Google models from general data only.

In advanced mode, Google's tags load before consent, set no cookies, and send cookieless pings without identifiers. Those pings continue after a decline. Google can use them to model conversions and behaviour, so your reports look more complete, with a modelled share.

Which to choose is partly a legal and policy question about whether sending cookieless pings without consent fits your privacy position. Many UK businesses choose advanced mode for the modelling, others choose basic mode to send nothing at all. Decide deliberately and describe your choice in your privacy notice. This is not legal advice.

Why numbers can drop after a correct setup

This is the part that causes the most worry. You fix the banner and consent mode, and the next week GA4 shows fewer users, fewer sessions and fewer conversions. It looks as if something broke.

Usually it means the opposite. Before, tags may have been setting cookies and counting people who had not agreed, or who had declined. Now they are not. The new, lower number is closer to what you are actually allowed to measure.

Expect fewer users and sessions in standard reports, a rise in traffic marked not set or unassigned, and ad platform conversions dropping if they previously counted visitors who declined. In advanced mode, GA4's behavioural modelling only applies once a property meets Google's thresholds, and modelled conversions can take days to show.

To tell a correct drop from a broken setup, check two things. Does the drop roughly match the share of visitors who decline on your banner? And do conversions from visitors who accepted still arrive with the right values? If both answers are yes, the setup is working.

How to check your setup

Open the site in a private window and, before choosing anything, check developer tools for Google cookies. There should be none in either mode. In the network tab, check that the default consent state is sent before any Google tag request.

Decline and browse, and confirm no Google cookies are set. In advanced mode, requests should show consent as denied. Accept and browse, and confirm cookies are set and requests show consent as granted. Check all four signals are set, including ad_user_data and ad_personalization.

Then check that tags from Meta, LinkedIn, TikTok, Hotjar and others also wait for consent, because consent mode does not control them. In Google Tag Manager, check each tag's consent settings match its purpose, and record your acceptance rate. You will need it to explain gaps between analytics and orders.

If your numbers dropped after a banner change and you are not sure whether to worry, a Discover audit checks the consent setup end to end and tells you whether the drop is a fault or simply accurate.