Consent Mode v2 GA4

🚨 Why This Matters Now

In March 2024, Google announced that Consent Mode V2 is now mandatory for sites using:

• Google Ads (retargeting or conversion tracking)
• GA4 with modeling
• Personalised ads in the EU

No Consent Mode? No data. It’s that simple.

🧠 Quick Recap: What Is Consent Mode?

Consent Mode lets Google know the user’s privacy choices. It doesn't set cookies until consent is granted, and fills in the gaps with modeled data if you're compliant.

V1 Parameters:

• ad_storage: Consent for advertising cookies
• analytics_storage: Consent for analytics cookies

V2 Adds Two New Fields:

• ad_user_data: Consent for sending user-level data (like remarketing lists)
• ad_personalization: Consent for personalising ads (e.g., demographics, interests)

Ignore these new fields and you’re effectively opting out by default.

🔥 What Happens If You Skip It

Your tags will still fire.

But your conversions? Gone.
Your remarketing lists? Empty.
Your LTV reporting? Useless.

You’ll see:

• 🚫 Modeled conversions disappear
• 🚫 “Blanks” in BigQuery session data
• 🚫 Targeting audiences in Google Ads collapse

⚙️ How GA4 Uses Consent Mode

GA4 uses Consent Mode to determine:

• Whether to fire tags
• Whether to collect raw event data
• Whether to model missing conversions and sessions

If your Consent Mode isn’t correctly set up:

• Modeling won’t trigger
• GA4 will drop data below threshold
• And your BigQuery will bleed with session gaps

🛠️ Setting Up Consent Mode V2 (Properly)

1. Connect a CMP

Use a compliant Consent Management Platform (CMP):

• Cookiebot
• OneTrust
• Axeptio
• Didomi

Make sure it:

• Can map to ad_storage, analytics_storage, ad_user_data, and ad_personalization
• Fires before any other tag

2. Deploy via GTM

You must split your tag firing logic:

javascript

CopyEdit

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

// After consent
gtag('consent', 'update', {
 ad_storage: 'granted',
 analytics_storage: 'granted',
 ad_user_data: 'granted',
 ad_personalization: 'granted'
});


3. Respect Consent Throughout

Especially important for:

• SPAs (Single Page Apps): Carry consent state across virtual page views
• Server-side GTM: Must forward consent state via the gtm.gcs query string

🧪 How to Check It’s Working

In GA4:

• Go to Admin > Data Settings > Data Collection
• Check "Consent Mode status" should say “Active”
• Look for modeled conversions in the attribution reports

In BigQuery:

Run a query:

sql

CopyEdit

SELECT consent_granted, COUNT(*) AS sessions
FROM `your_dataset.your_table`
WHERE event_name = 'session_start'
GROUP BY consent_granted


⚰️ The Top 5 Mistakes That Kill Consent Mode

1. You don’t pass ad_user_data and ad_personalization at all
2. Your tags fire before consent is recorded
3. You only use ad_storage and analytics_storage (outdated)
4. Your CMP is not Google-certified
5. Your site uses an SPA and doesn't persist consent

📊 Pro Tip: Show the Business the Impact

Don’t sell Consent Mode as "compliance". Sell it as:

• Revenue protection
• Attribution survival
• Google Ads eligibility

Show the modeled vs. non-modeled difference in GA4. Use BigQuery to prove how many conversions you'd lose without it.

✅ TL;DR – Your Consent Mode V2 Checklist

• ✅ Use a CMP with V2 support
• ✅ Pass all 4 consent fields via gtag or GTM
• ✅ Validate consent status in GA4 & DebugView
• ✅ Check for modeling drop-off post-implementation
• ✅ Run a BQ query to track consent-granted vs denied sessions

🎯 Final Word

This isn’t just a privacy update.

This is the new frontline for data collection, attribution, and ad performance.
If your Consent Mode isn’t right, your entire stack is broken and your marketing budget is being flushed without you knowing it.

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