GTM Custom Trigger Setup Based on Gravito GCM Consents

Overview

Gravito CMP pushes consent updates using a custom event named gravitoGCMConsents. Each consent value is available under consent.* in the dataLayer.

This guide explains how to:

  • Create Data Layer Variables (DLVs)
  • Create Custom Event triggers
  • Map consent categories to GCM signals
  • Fire tags based on consent
Cookie Consent Category GCM v2 Values
Necessary security_storage
Analytics analytics_storage
Functional functionality_storage, personalization_storage
Marketing ad_storage, ad_user_data, ad_personalization

Step 1: Create Data Layer Variables

Go to GTM UI:

  1. Navigate to Variables
  2. Click New under User-Defined Variables
  3. Click Variable Configuration
  4. Select Data Layer Variable

Create variables for the following:

  • consent.security_storage
  • consent.analytics_storage
  • consent.functionality_storage
  • consent.personalization_storage
  • consent.ad_storage
  • consent.ad_user_data
  • consent.ad_personalization

Example:

Name: DLV - consent.analytics_storage
Data Layer Variable Name: consent.analytics_storage
Version: Version 2

Step 2: Create Custom Event Trigger

  1. Go to Triggers
  2. Click New
  3. Select Custom Event

Configuration:

Name: CE - Gravito GCM Consents
Event Name: gravitoGCMConsents
Trigger fires on: All Custom Events

Step 3: Create Category-Based Triggers

Analytics Trigger

  1. Go to Triggers → New
  2. Select Custom Event

Name: CE - Analytics Granted
Event: gravitoGCMConsents

Condition: DLV - consent.analytics_storage equals granted

Marketing Trigger

Name: CE - Marketing Granted
Event: gravitoGCMConsents

Condition (strict): DLV - consent.ad_storage equals granted
AND
DLV - consent.ad_user_data equals granted
AND
DLV - consent.ad_personalization equals granted

Functional Trigger

Name: CE - Functional Granted
Event: gravitoGCMConsents

Condition: DLV - consent.functionality_storage equals granted

OR

DLV - consent.personalization_storage equals granted

Necessary Trigger

Name: CE - Necessary Granted
Event: gravitoGCMConsents

Condition: DLV - consent.security_storage equals granted

Step 4: Attach Triggers to Tags

  1. Go to Tags
  2. Select a tag
  3. Click Triggering
  4. Add the relevant trigger

Example:

  • Analytics Script → CE - Analytics Granted
  • Marketing Pixel → CE - Marketing Granted
  • Functional Script → CE - Functional Granted

Step 5: Testing

  1. Click Preview in GTM
  2. Open your website
  3. Trigger consent changes

Verify:

  • Event gravitoGCMConsents is fired
  • Variables show correct values
  • Tags fire only when consent is granted

Final Flow

Gravito CMP → dataLayer (consent values)\ → GTM Variables
→ Custom Event Trigger
→ Conditional Trigger
→ Tag Fires

Example

The following script delays the initialization of Google Analytics 4 (GA4) until the default Google Consent Mode (GCM) consent is received. The Gravito CMP dispatches an event when the default consent values are added to the dataLayer.
This script listens for that event and initializes GA4 only after the consent information becomes available.
This script must be placed inside the section of the document, and the original GA4 initialization script should be removed to prevent GA4 from loading before the default consent is applied.


   <script>
      document.addEventListener("gcmConsentUpdated", (event) => {

        let ga4Script = document.createElement("script");
        ga4Script.src =
          "https://www.googletagmanager.com/gtag/js?id=<Unique_ID>";
        ga4Script.async = true;
        document.head.appendChild(ga4Script);
        if (!gtag) {
          window.dataLayer = window.dataLayer || [];
          function gtag() {
            dataLayer.push(arguments);
          }
        }
        gtag("js", new Date());

        gtag("config", "<Unique_ID>", {
          send_page_view: false,
        });
      });
    </script>