Aggregated Event Measurement: Prioritizing Your 8 Events

Meta gives you exactly 8 conversion events per domain. Not 10, not 20—eight. These 8 events are all you get for iOS 14+ attribution under Apple's privacy framework. Choose wisely, because the events you prioritize determine which conversions Meta can track, attribute, and optimize for. Choose wrong, and you're flying blind on your most valuable user actions.

Aggregated Event Measurement (AEM) is Meta's protocol for working within Apple's App Tracking Transparency restrictions. Understanding how it works—and how to configure it correctly—is essential for any advertiser serious about iOS measurement in 2025.

What Is Aggregated Event Measurement?

AEM is Meta's response to Apple's privacy changes. When iOS users opt out of tracking (about 75% do), Meta can't receive conversion events through normal pixel tracking. AEM provides a limited pathway: you can still track up to 8 events per domain for these users, but with restrictions.

How AEM Works

When an opted-out iOS user converts, Apple's system captures the event and reports it to Meta through their Private Click Measurement framework. But Apple limits this to one conversion event per user per 24-hour period, and only your highest-priority event is reported.

Example: User clicks your ad, lands on your site, views a product, adds to cart, then purchases—all within one session. Under AEM, only one event gets reported. If Purchase is your highest priority (which it should be), that's the event Meta sees. ViewContent, AddToCart—invisible.

The 8-Event Limit

You configure up to 8 events per domain in Events Manager. These events are ranked by priority (1 = highest). When multiple events occur in a single attribution window, only the highest-priority event is reported. Events not in your top 8 aren't tracked for opted-out iOS users at all.

Why AEM Event Selection Matters

Impact on Attribution

Events outside your top 8 won't show conversions from opted-out iOS users. If you're running campaigns optimized for an event that isn't prioritized, Meta has no conversion data to optimize against for 75% of iOS users.

Impact on Optimization

Meta's algorithm learns from conversions. If your Purchase event is properly configured in AEM, the algorithm receives iOS purchase signals. If it's not, the algorithm only sees non-iOS conversions—learning from an unrepresentative sample.

Impact on Reporting

Your conversion reports will systematically undercount events not in your AEM configuration. This skews ROAS calculations and makes it impossible to accurately evaluate campaign performance.

How to Configure AEM Events

Step 1: Verify Your Domain

Before configuring events, you must verify domain ownership in Business Settings. Go to Business Settings → Brand Safety → Domains. Add your domain and complete DNS or meta-tag verification. This is required for AEM to work.

Step 2: Access Events Manager

Go to Events Manager in your Meta Business Suite. Select your pixel/dataset. Click "Aggregated Event Measurement" in the left sidebar.

Step 3: Configure Events

Click "Configure Web Events" and select your verified domain. You'll see the option to add up to 8 events. Drag to reorder by priority (top = highest priority).

Step 4: Assign Values (Optional)

For events like Purchase, you can configure value optimization. This tells Meta to optimize not just for conversions but for conversion value—critical for e-commerce.

Prioritizing Your 8 Events: The Framework

Principle 1: Bottom of Funnel First

Highest priority should go to your most valuable conversion events. For most businesses, this is Purchase or Lead. These are the events you're actually optimizing for, so they need full iOS coverage.

Principle 2: Campaign Objectives Second

After your primary conversion, prioritize events you run campaigns against. If you have separate campaigns optimizing for AddToCart (for upper-funnel), that event needs AEM coverage.

Principle 3: Reporting Needs Third

Events you want to track for reporting but don't optimize against come lower. ViewContent might be useful for understanding funnel health, but it's less critical than Purchase.

Recommended Event Configurations by Business Type

E-commerce (Standard)

Lead Generation

SaaS / Subscription

Common AEM Configuration Mistakes

Mistake 1: PageView at Priority 1

Some advertisers leave default settings with PageView as highest priority. This means when a user views a page and purchases, only the PageView is reported—Purchase is lost. Always put your conversion event first.

Mistake 2: Too Many Custom Events

If you've created custom events (ButtonClick, VideoWatch, etc.), you only have 8 slots. Custom events compete with standard events. Use standard events where possible—they're automatically recognized and don't consume limited slots for minor interactions.

Mistake 3: Not Configuring Value Optimization

For Purchase events, enabling value optimization tells Meta to optimize for revenue, not just conversion count. Without it, a $10 purchase counts the same as a $1000 purchase in optimization.

Mistake 4: Forgetting Domain Verification

AEM requires domain verification. Unverified domains can't configure events. If you recently changed domains or are running multiple brands on separate domains, verify each one.

Mistake 5: Not Aligning with Campaign Objectives

If you run AddToCart optimization campaigns but AddToCart isn't in your AEM events, those campaigns can't receive iOS conversion signals. Match your AEM configuration to your actual campaign strategy.

Managing Multiple Domains

Each domain gets its own 8 events. If you operate multiple brands or storefronts on different domains, you must configure AEM separately for each.

Subdomains

Subdomains typically share the parent domain's AEM configuration. shop.example.com and blog.example.com both fall under example.com's 8 events. Plan accordingly.

Domain Changes

If you migrate to a new domain, you'll need to verify the new domain and reconfigure AEM. There's a 72-hour delay after changing AEM configuration before it takes effect—plan migrations carefully.

AEM and Conversion Value

For e-commerce, conversion value matters as much as conversion count. AEM supports value optimization, but setup is specific.

Configuring Value Optimization

When adding Purchase to your AEM events, enable "Value Optimization" in the configuration. You can choose to send actual values (dynamic) or use preset value ranges. Dynamic values are more accurate but require proper implementation in your tracking code.

Value Tiers

If you can't pass dynamic values, Meta lets you define value tiers. For example: Tier 1 = $0-50, Tier 2 = $50-150, Tier 3 = $150+. Each conversion is bucketed into a tier, preserving some value signal without exact amounts.

Monitoring AEM Health

Check Event Configuration Regularly

Events Manager shows your current AEM configuration. Verify it monthly, especially after site changes, tracking updates, or campaign strategy shifts.

Compare iOS vs. Non-iOS

If iOS conversion rates are dramatically lower than Android/desktop and you've confirmed tracking is working, your AEM configuration might be missing key events. Cross-reference which events are being tracked.

Audit After Changes

Any change to AEM configuration has a 72-hour delay. After making changes, wait 72 hours, then audit conversion data to confirm events are being received as expected.

AEM and Campaign Structure

Your AEM configuration should inform campaign structure:

Optimize for Events in Your Top 8

Only run optimization campaigns for events that are in your AEM configuration. Optimizing for an event not in the top 8 means the algorithm has no iOS signal for 75% of users.

Consider Simplifying

If you previously ran campaigns optimized for 10+ different events, consolidate. Focus on 2-3 primary conversion events that are in your AEM top 8.

Use Standard Events

Standard events (Purchase, Lead, AddToCart) work seamlessly with AEM. Custom events require extra configuration and consume limited slots. Where possible, map your conversions to standard events.

The 72-Hour Delay

AEM configuration changes take up to 72 hours to propagate. During this period:

• Old configuration continues to apply
• Campaign optimization uses previous settings
• New events aren't tracked until propagation completes

Plan configuration changes during low-traffic periods. Avoid major changes right before peak sales days (Black Friday, launches) when you need stable tracking.

Key Takeaways

• AEM limits you to 8 conversion events per domain for iOS 14+ users
• Only the highest-priority event is reported when multiple occur
• Put your primary conversion (Purchase, Lead) at priority 1
• Domain verification is required—complete it before configuring events
• Campaign optimization objectives must align with AEM-configured events
• Configuration changes have a 72-hour delay—plan accordingly
• Value optimization is essential for e-commerce—enable it for Purchase

FAQ

Can I track more than 8 events?

Yes, but only for non-iOS users and iOS users who opted into tracking (about 25%). Events outside your top 8 are invisible for opted-out iOS users—roughly 55-60% of your mobile traffic.

What happens if I don't configure AEM at all?

Meta uses default configuration, typically with PageView at highest priority. This means Purchase events from opted-out iOS users may not be reported, devastating your conversion data.

Does AEM affect Android users?

No. AEM only applies to iOS 14.5+ users who opted out of tracking. Android users, iOS users who opted in, and desktop users are tracked normally without the 8-event limit.

How do I know if my AEM is working?

Check Events Manager for iOS-specific conversion data. If you see iOS conversions for your priority events, AEM is working. If iOS shows near-zero conversions while Android shows normal, you have a configuration issue.

Can I change my AEM configuration frequently?

Technically yes, but each change has a 72-hour delay. Frequent changes mean constant flux in tracking. Set your configuration based on long-term strategy and only change when campaign strategy genuinely shifts.