We were launching a project in Europe. Everything was neat and legal:
Cookie banner?
Consent Mode?
Set up just like the docs said.
A couple of weeks later, I opened up GA4… and thought, Wait, where did everyone go? Traffic was down, conversions disappeared into the abyss, paid channels looked like a black hole. Everything was technically working — just not the way we expected.
Welcome to the magical world of ConsentMode.
For those who haven’t met this beast yet: Consent Mode is a Google technology that adjusts how Google tags (like GA4, GoogleAds, etc.) behave based on whether a user gives consent for cookies.
If a user says yes — you get full data, business as usual. If they say no — tags still fire, but without cookies. That means you get stripped-down, anonymous data (no client_id, no session_id), and Google’s algorithms try to fill in the blanks with modeling magic.
So yeah, Consent Mode isn’t just a simple “on/off” switch. It’s more like a smart toggle that helps you walk the fine line between privacy regulations (hi, GDPR) and useful analytics.
Consent Mode doesn’t just change what data you get — it changes how it’s collected and interpreted.
And that brings a few important caveats:
1. If a user doesn’t give consent, you still get some event data — just not the usual kind. It’s trimmed down, anonymized, and missing IDs.
2. That incomplete data gets thrown into a model that tries to guess what really happened.
3. In GA4, modeled and real events look exactly the same. No labels, no warnings, just vibes.
4. Reports in GA4, Google Ads, and BigQuery can start telling very different stories — and you won’t always know why.
You open GA4 and think: “Oh no, our conversions disappeared!” Spoiler: they didn’t. Google’s model just painted you a nice little picture… based on assumptions.
So how do I keep my sanity with Consent Mode? Here are my go-to rules:
1. Be smart with your banners. Ask for consent only where legally required. No need to scare off data from users who didn’t even need a cookie banner.
2. Add anonymous parameters to your events. That way, even with no consent, you can still collect useful signals — and keep a grip on reality.
3. Separate fact from fiction. In BigQuery, use the analytics_storage field to see which data is real and which might be modeled.
4. Track how many people are actually clicking “OK.” If consent rates are low, it might be your banner’s fault — tweak the wording, design, behavior, whatever it takes.
Consent Mode isn’t the villain. It’s just playing by a different rulebook. Think of it as a fragile truce between the law, user privacy, and your desire for clean, reliable data. Like any compromise, it can work — as long as you know what you’re working with.
If you work with GA4 to BigQuery exports, be sure to check out my SQL cheat sheet.
