Aggregated Event Measurement (AEM)
Aggregated Event Measurement is Meta’s framework for measuring conversions from users who opt out of tracking (notably on iOS): a limited number of prioritized events are measured in aggregate, privacy-preserving form rather than at the individual level.
AEM is Meta’s response to Apple’s App Tracking Transparency. Because opted-out users cannot be measured individually, Meta lets you rank a limited set of conversion events per domain and reports them in aggregate with modeling. Getting the event prioritization right — putting your true primary conversion at the top — is a real configuration task with real performance consequences.
AEM is why domain verification and correct event configuration matter so much post-iOS, and why value optimization can be constrained for opted-out traffic. It is a background constraint operators should understand even though it is mostly configured once and left alone.
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