Aggregated Event Measurement (AEM) is Meta's framework for measuring web conversions from iOS users who opt out of tracking, within Apple's privacy limits. It caps each domain to eight prioritized conversion events, which forces you to choose what matters.
Why it exists
After Apple's App Tracking Transparency, Meta cannot track opted-out iOS users the old way. AEM reports their conversions in aggregate, and limits each verified domain to eight events ranked by priority. Only the highest-priority event for a user is counted.
What it forces
You have to rank your eight events deliberately, putting purchase or qualified-lead above shallow ones, because the order decides what gets measured and optimized for opted-out traffic. It is also why server-side tracking and strong event match quality matter more than ever.