When Apple introduced iOS 14.5, it changed how ad platforms could track users on Apple devices. For Meta advertisers, this meant a fundamental shift in how conversions are measured — and it introduced a system called Aggregated Event Measurement (AEM) that every advertiser needs to understand.
If you have seen warnings in your Meta Pixel or Events Manager about domain verification or event configuration, this is why. This guide explains exactly what Aggregated Event Measurement is, how the 8-event limit works, and how to configure it correctly so you do not lose iOS conversion data.
What Is Meta Aggregated Event Measurement?
Meta Aggregated Event Measurement (AEM) is Meta’s framework for measuring conversions from iOS users who have opted out of tracking under Apple’s App Tracking Transparency (ATT) policy. Rather than tracking individual users, AEM uses aggregate, anonymised data to model conversions at the campaign level.
Under iOS 14+, when a user opts out of tracking, Meta can no longer associate their in-app actions with specific ad clicks using the IDFA. AEM works around this by:
- Limiting advertisers to 8 configurable events per verified domain
- Using statistical modelling to estimate conversions for opted-out users
- Reporting aggregate results with a delay of up to 3 days for some events
In practice, this means your reporting window shortened, real-time data is less accurate for iOS traffic, and you need to deliberately choose which 8 events matter most to your business.
Why Domain Verification Is a Prerequisite
Before you can configure your 8 events, Meta requires you to verify ownership of your domain. This prevents one Business Manager from overriding another business’s event configuration.
To verify your domain:
- Go to Meta Business Suite → Brand Safety → Domains
- Add your root domain (e.g., yourdomain.com — not a subdomain)
- Choose one verification method: DNS TXT record, HTML meta tag, or file upload
- Add the verification to your website
- Click Verify in Meta
Once verified, you can configure your event priority. Note that only the root domain owner can set event priority. If you use a platform like Shopify that has already claimed domain ownership, you may need to contact Meta support to resolve the conflict.
Understanding the 8-Event Limit
AEM allows you to configure up to 8 pixel events per verified domain, ranked in priority order. The priority order matters because when a user performs multiple events in a single session, only the highest-priority event is reported for that session.
For example, if a user adds to cart, initiates checkout, and then purchases, only the Purchase event gets reported — assuming Purchase is your number 1 priority. This is by design to avoid double-counting conversions for a single session.
Events you do not configure in AEM will still fire in your pixel and still appear in Events Manager for non-iOS users. But for opted-out iOS users, unconfigured events may not be attributed back to a specific ad campaign and cannot be used as optimisation goals.
How to Configure Your 8 Events in Meta Events Manager
- Go to Events Manager in Meta Business Suite
- Select your pixel
- Click Aggregated Event Measurement in the left sidebar
- Click Configure Web Events
- Select your verified domain
- Add events in priority order — drag to reorder
- Click Apply to save
Changes take effect within 72 hours. During this window, campaigns targeting iOS users may see disrupted reporting. Avoid making AEM changes during peak sale periods or when a campaign is still in the learning phase.
Choosing the Right Event Priority Order
Your priority order should reflect what matters most to your business. Always put your primary conversion goal at position 1. Here are recommended configurations by business type:
For Ecommerce Stores
| Priority | Event | Why |
|---|---|---|
| 1 | Purchase | Highest value, what bidding optimises toward |
| 2 | InitiateCheckout | Strong purchase intent signal |
| 3 | AddToCart | Mid-funnel engagement |
| 4 | ViewContent | Product page engagement for retargeting |
| 5 | Search | Intent signal for catalogue campaigns |
| 6 | AddPaymentInfo | Checkout abandonment signal |
| 7 | CompleteRegistration | Account creation |
| 8 | Contact | Lead capture |
For Lead Generation Businesses
| Priority | Event | Why |
|---|---|---|
| 1 | Lead | Primary conversion goal |
| 2 | CompleteRegistration | High-intent form submission |
| 3 | Contact | Call or chat initiated |
| 4 | Schedule | Booking made |
| 5 | ViewContent | Service page viewed |
| 6 | Search | On-site search |
| 7 | Subscribe | Email list signup |
| 8 | PageView | Top-of-funnel awareness |
AEM and the Conversions API: How They Work Together
The Conversions API (CAPI) and AEM are complementary systems. CAPI sends conversion data from your server rather than the browser, which means it is not blocked by iOS restrictions or ad blockers. When used together:
- Browser pixel captures events from users who allow tracking
- CAPI captures events from all users including those who block browser tracking
- AEM determines how Meta models and reports iOS conversions in Ads Manager
If you are using server-side tracking via CAPI, you still need to configure AEM. The two systems serve different purposes: CAPI improves data collection; AEM determines how that data is reported and attributed for opted-out iOS users. You must configure both to get accurate iOS reporting.
Impact on Your Ads Manager Reporting
After setting up AEM correctly, expect these changes to your reporting:
- Conversion counts may increase slightly — Meta’s modelling often recovers iOS conversions that were previously invisible
- Real-time reporting data will have a 24 to 72 hour delay for some iOS traffic
- Your reported ROAS may shift as iOS attribution becomes more accurate
- Campaign optimisation for iOS-heavy audiences will improve over 1 to 2 weeks as the algorithm adapts
Common AEM Mistakes to Avoid
- Not verifying your domain — without domain verification, you cannot configure event priority and AEM will not work correctly
- Putting PageView at priority 1 — this wastes your top slot on a low-value signal; your primary conversion goal should always be number 1
- Changing event priority mid-campaign — updating your AEM configuration disrupts active campaigns and causes a reporting gap during the 72-hour transition period
- Assuming AEM covers everything — AEM applies to opted-out iOS users only. For all other users, standard pixel tracking still applies
- Skipping deduplication setup — if you are using both pixel and CAPI, deduplication must be configured to avoid overcounting in your AEM-reported conversions
Run a tracking audit two weeks after configuring AEM to confirm your Purchase event volume accurately reflects in Events Manager and matches your order management system. The 5-minute Facebook pixel audit guide covers the exact steps to verify this.
Related Articles
- How to Audit Your Facebook Pixel in 5 Minutes
- Meta Pixel vs Conversions API: Which One Do You Actually Need?
- Tracking Explained: How Every Ad Platform Tracks Your Ads
- Free Tracking Audit Checklist: Is Your Setup Working?
📋 Not sure where to start? Use our Free Tracking Audit Checklist to find out where your setup is losing data.
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