GTM & Google Consent Mode v2

Google Consent Mode v2 lets you tell Google's tags how to behave when a visitor hasn't consented to tracking. Consenti pushes the right signals to your dataLayer automatically — you just configure a container ID and GTM handles the rest.

Why this matters

Without Consent Mode, Google Ads and Analytics tags fire unconditionally. With Consent Mode v2, they receive a consent state (granted or denied) and adjust their behaviour — firing in cookieless mode or not firing at all. This is required for EU compliance from March 2024 for conversion modelling in Google Ads.

Step 1 — Add GTM config to Consenti

import { ConsentiSetup } from '@consenti/ui'

new ConsentiSetup({
  compliance: { type: 'opt-in' },
  utils: {
    gtm: {
      containerId: 'GTM-XXXXXX',    // your GTM container ID
      urlPassthrough: true,          // preserve click IDs (gclid/fbclid) for cookieless modelling
      adsDataRedaction: true,        // redact ad click IDs when ad_storage is denied
    },
  },
})

That's it. Consenti injects the GTM snippet, calls gtag('consent', 'default', …) immediately with a denied-by-default state, then calls gtag('consent', 'update', …) each time the visitor submits consent.

What gets pushed to dataLayer

Consenti calls the real gtag() consent API — via the standard stub-queue pattern, so it works whether your own gtag.js/GTM snippet loads before or after Consenti. Each call ultimately becomes a dataLayer.push([...]) entry:

// On page load — before visitor interaction
gtag('consent', 'default', {
  analytics_storage: 'denied',
  ad_storage: 'denied',
  ad_user_data: 'denied',
  ad_personalization: 'denied',
  functionality_storage: 'granted',
  personalization_storage: 'denied',
  security_storage: 'granted',
})

After the visitor submits their preferences:

// On consent submission
gtag('consent', 'update', {
  analytics_storage: 'granted',
  ad_storage: 'denied',
  ad_user_data: 'denied',
  ad_personalization: 'denied',
  functionality_storage: 'granted',
  personalization_storage: 'denied',
  security_storage: 'granted',
})

// Plus, when configured:
gtag('set', 'url_passthrough', true)
gtag('set', 'ads_data_redaction', true) // true when ad_storage is denied

Reading GTM-format consent in your code

Use widget.getGTMConsent() to read the current consent state in the exact format GTM expects — useful for debugging or for sending to your own analytics endpoint.

const widget = new ConsentiSetup({ /* ... */ })

const gtmConsent = widget.getGTMConsent()
// {
//   analytics_storage: 'granted',
//   ad_storage: 'denied',
//   ad_user_data: 'denied',
//   ad_personalization: 'denied',
//   functionality_storage: 'granted',
// }

Verifying in GTM Preview

1. Open your site with GTM Preview active (click “Preview” in GTM).
2. Reload the page. In the GTM debug panel, you should see a consent_default event with all values denied.
3. Accept cookies on the banner. You should see a consent_update event with the values reflecting your choices.
4. Check that tags configured to fire “On Consent” now fire (e.g. GA4 config tag).

Frequently asked questions