Your Cookie Banner Shows Up. Are the Cookies Already Loaded? (5-Minute DevTools Test)

Flora Wilson — Thu, 15 Oct 2026 10:47:39 +0000

TL;DR: A cookie banner can appear on screen while tracking cookies load behind it. Test yours in DevTools, set Google's consent defaults to denied, and let a consent platform release tags only after a visitor chooses.

The problem you get asked to fix

Marketing says the numbers look off. Legal asks if the site is compliant. Both questions often lead to the same place: the banner shows, but the tags don't wait for it.

That gap is what the UK regulator, the ICO, tested for when it reviewed the top 1,000 UK websites in 2025. Its checks included advertising cookies stored before a visitor could choose, and advertising cookies placed when a visitor hadn't agreed.

Test yours in five minutes

Open your site in a private window.
Before touching the banner, open DevTools, go to Application > Cookies and select your domain.
Look for tracking cookies such as _ga (Google Analytics) or _fbp (Meta Pixel).
Click Reject, reload the page and check again.

If those cookies appear before a choice or after Reject, the banner is only for show.

Set Google's defaults first

Google's consent mode docs say the default command must run on each page before any command that sends measurement data:

gtag('consent', 'default', {
  'ad_storage': 'denied',
  'ad_user_data': 'denied',
  'ad_personalization': 'denied',
  'analytics_storage': 'denied'
});

When a visitor accepts, your consent platform sends a gtag('consent', 'update') command with the same four keys set to 'granted'.

Why it matters beyond compliance

Tags that respect choices give marketing data it can rely on, and consent signals let Google model conversions it can't observe. It's one of the reasons cookie banners matter to the people reading the reports as much as to legal.

Where Seers AI fits