Aggregated Event Measurement (AEM) is the protocol Meta built in 2021 to keep measuring web and app conversions after Apple's App Tracking Transparency rules let iOS users opt out of tracking. It aggregates and limits the data Meta uses about people who opted out, so Meta can still report and optimise conversions without tracking individuals across apps and websites.
How AEM used to work
When AEM launched, every advertiser had to configure it in Events Manager:
- Domain verification for each website domain in your business account.
- Up to eight conversion events per domain, ranked in order of priority.
- Only the highest-priority event a person completed was counted for people who opted out of tracking on iOS.
- Changing the ranking could pause campaigns for up to three days.
Many older guides still describe this setup in detail.
What has changed
Meta has since removed most of that manual work for web events. Starting in 2023 it announced that event prioritisation and domain verification were no longer required for event configuration, and the AEM tab has disappeared from Events Manager in most accounts as the change rolled out through 2025. Meta now aggregates eligible web events automatically.
What that means for you, at the time of writing:
- You no longer need to rank eight web events to run conversion campaigns in most accounts.
- You can optimise for events that previously didn't fit in your top eight.
- The privacy limits on data from people who opted out still apply. Meta still models some conversions and reports them with delays and less detail.
- For iOS app events, prioritised event configuration still applies in many cases, alongside Apple's SKAdNetwork.
Meta rolls changes out unevenly, so if your Events Manager still shows an event configuration screen, follow it.
What still matters for tracking quality
AEM doesn't fix weak data. These steps matter more than any event ranking:
- Run the Meta Pixel and the Conversions API together, with event deduplication.
- Send customer information, such as hashed email and phone, to raise event match quality.
- Send value and currency with every Purchase event.
- Expect some gap between Meta's numbers and your store's, and judge totals with MER.
Common mistakes
- Following old AEM tutorials and looking for settings that no longer exist.
- Assuming AEM removal means full tracking returned. The opt-out limits are still there.
- Ignoring app events. If you advertise an iOS app, check app event configuration separately.
Our guide to Meta Pixel and Conversions API on Shopify covers a clean tracking setup.
Frequently asked questions
What is Aggregated Event Measurement on Facebook?
Aggregated Event Measurement is Meta's protocol for measuring conversions from people who opted out of tracking, introduced in 2021 for Apple's iOS 14.5 App Tracking Transparency rules. It limits and aggregates data about opted-out users so Meta can still report and optimise conversions.
Is the 8-event limit still in place?
For web events, Meta has removed the manual eight-event configuration in most accounts. It announced the change in 2023 and the AEM tab has disappeared from Events Manager as it rolled out. iOS app events can still use prioritised configuration.
Do I still need to prioritise events in Events Manager?
In most accounts, no, for web events. If your Events Manager still shows an event configuration or prioritisation screen, follow it, because Meta rolls changes out unevenly. App advertisers should check app event settings separately.
Does AEM still affect my reporting?
Yes. The privacy limits on data from people who opted out of tracking still apply, so some conversions are modelled, delayed or reported with less detail. Strong Conversions API data and event match quality reduce the gap.
