How Consent Mode works mechanically
Consent Mode sits between your cookie banner and your Google tags. When a visitor accepts cookies, the tags work normally and conversions are measured directly. When a visitor declines, the tags switch behavior: no advertising cookies are set, but anonymous pings can still flow.
Those cookieless signals feed Google's conversion modeling, which estimates the conversions that consented measurement could not see. The result is a conversion count that combines observed and modeled data. It is less precise than full measurement, but far better than the alternative, which is declined visitors disappearing from the data entirely. The visitor's choice is respected either way; the difference is whether the advertiser keeps usable measurement.
Why v2 is effectively mandatory in the EU
Since March 2024, Consent Mode v2 is effectively mandatory for advertisers targeting the EU. Without it, Google Ads loses audience features, including remarketing, and conversion measurement degrades badly. An EU advertiser running without a correct v2 implementation is competing with structurally worse data than every competitor who set it up properly.
This is a platform requirement, not a legal opinion. The consent banner handles the regulatory side; Consent Mode is what tells Google's tags about the choice the visitor made, and v2 is the version Google requires for full functionality.
Where setups go wrong, and what to check
The dangerous failure mode is silent. A misconfigured banner that blocks tags regardless of consent, or tags firing in the wrong consent states, cuts conversion data without any error message. In the dashboard it looks identical to a performance drop, so the response is often a strategy change that fixes nothing.
The setup needs three things verified: the banner integrates correctly with Consent Mode, the tags fire in the right consent states, and the whole flow is tested rather than assumed. For EU e-commerce stores, a Consent Mode check belongs in every tracking audit, because it is one of the most common silent measurement killers. Place one test conversion in each consent state and watch where it lands.