Consent Mode v2 in the UK: signals, basic vs advanced and pitfalls

If you advertise to people in the UK, Google’s EU user consent policy applies to you, despite the name: it covers end users in the EEA, the UK and Switzerland. A Consent Mode v2 UK set-up is how Google’s tags receive each visitor’s choice, passed as four signals that decide what those tags may store and send.

The policy requires legally valid consent and doesn’t name Consent Mode as the only mechanism, with TCF as an alternative. This guide is a developer’s view of how the thing works and where it breaks, and none of it is legal advice.

What are the four Consent Mode v2 signals?

Version 2 added the last two in this table, and those are the two most often forgotten.

A banner integration written before those last two existed can carry on looking perfectly healthy while ad_user_data is never updated. The visible symptom turns up somewhere else entirely, usually as enhanced conversions reporting partial or no data, and nobody connects the two.

What is the difference between basic and advanced consent mode?

The difference is what happens before and after a visitor says no.

With basic consent mode, tags are blocked until the visitor interacts with the banner. If they decline, nothing is sent. It’s simple to explain and simple to check, and you get no measurement at all from the people who refuse.

With advanced consent mode, tags load straight away and send cookieless measurements while consent is denied. Those measurements support more detailed modelling, so Google has more to go on when estimating the conversions it can’t observe directly.

Should you use basic or advanced consent mode?

Take these questions in order and stop at the first one that settles it.

1. Has whoever owns your privacy position agreed to tags loading before a choice is made? If not, use basic. Advanced sends cookieless requests while consent is denied, and whether you’re comfortable with that is a question for your legal advisers.
2. Can your banner set defaults before any tag runs? If not, sort that out before choosing, because neither mode behaves reliably without it.
3. Does your Google Ads account depend on Smart Bidding? If it does and a fair number of visitors decline, advanced gives the modelling more to work with.
4. Are your conversion volumes small? Modelling may have very little to go on, so a clean basic set-up is often the more sensible choice.

Our usual recommendation is advanced for businesses that rely on Smart Bidding, provided the first question has a documented yes and the banner loads in the right order. Everyone else is better served by a properly built basic set-up than by an advanced one that’s half finished.

Does Consent Mode make you compliant in the UK?

No. Consent Mode passes the visitor’s decision to Google’s tags, and it has no opinion on whether that decision was validly obtained. Compliance depends on your banner, your wording and what your site actually does before someone chooses.

Under PECR, non-essential cookies need active, clear consent and advertising cookies aren’t exempt. The UK rules are being updated, so check the ICO’s current guidance and take advice on your own position, whatever any blog tells you, this one included.

How does Consent Mode usually go wrong?

Run your own site against this list. Each item can be present on a site with a professional-looking banner.

• Defaults not set. Google’s own help pages are inconsistent about default states, so don’t rely on an assumed behaviour. Set all four signals explicitly, as denied, until the visitor has chosen.
• The banner firing after the tags. Default states have to be in place before any Google tag runs. A banner script that loads late, or a GTM tag on an ordinary page view trigger, gets this backwards, which is a bit like asking permission from the driveway with the van already loaded. In GTM, use the Consent Initialization trigger.
• ad_user_data missing. The banner updates the two original signals and ignores the newer ones, which quietly removes hashed data from your conversions.
• The UK left out of a region list. Defaults scoped to named countries sometimes cover the EU and forget GB.
• No update after the choice. The banner stores the decision in its own cookie but never sends the update to Google’s tags.
• Returning visitors forgotten. The choice is honoured on the first page and not replayed on the next one or on later visits.
• Tags outside the system. A hard-coded snippet or a plugin’s own tag loads regardless of what GTM has been told.

How do you check your Consent Mode set-up?

You can get a long way with a private browser window and Tag Assistant.

1. Open the site in a private window with Tag Assistant connected, and don’t touch the banner.
2. Find the first event and confirm all four signals show a default state.
3. Open your browser’s storage panel and confirm no advertising cookies have been set.
4. Click reject and confirm the update shows the signals as denied.
5. Start a new private window, click accept and confirm all four move to granted, including ad_user_data and ad_personalization.
6. Move to a second page and confirm the choice is still applied.
7. Look at the requests going to Google, where the gcs parameter reflects the storage consent state being reported.

If step 2 shows nothing, fix that before you look at anything else, since every other result depends on it.

What does consent do to your Google Ads data?

Expect your observed numbers to be lower than they’d be without a banner, because some visitors will refuse and that’s their right. The aim of a good set-up is to make sure every visitor who agrees is measured properly, and that those who don’t are treated as they asked.

Consent also affects features that look unrelated. Enhanced conversions and remarketing both depend on the signals above, and routing your tags through your own domain doesn’t change any of this. If you’re looking at Google tag gateway, Google’s instruction to turn off automated script set-up when you use consent mode applies to you.

Where we fit in

We wire up the technical side: signal defaults, banner timing, region handling and testing, built in your own GTM account as part of our Consent Mode v2 setup. The wording of your banner and your legal position stay with you and your advisers, as they should.

If you’re not sure which of the problems above you’ve got, get in touch for a chat or ask about the Tracking Audit, which checks your Consent Mode alongside the rest of your tags.