Facebook Aggregated Event Measurement: What Still Applies in 2026

Facebook Aggregated Event Measurement (AEM) is Meta's protocol for measuring web and app events from people using iOS 14 and later devices, with privacy protections such as identifier removal, differential privacy, and aggregation across users. It was introduced after Apple's App Tracking Transparency made opted-out iOS 14.5+ users invisible to IDFA. If you are looking for the old setup guide - domain verification, 8-event prioritization, the AEM tab in Events Manager - that workflow no longer exists. This article explains what changed, what the protocol still does, and how server-side events are treated.

What Is Facebook Aggregated Event Measurement?

Before iOS 14.5, the Meta Pixel fired conversion events without event-level limits, and attribution was deterministic. After Apple enforced ATT (mandatory from iOS 14.5), users who opt out of tracking can no longer be identified by IDFA, so Meta built Aggregated Event Measurement to recover limited measurement of those conversions. The protocol processes events with privacy protective measures - removing identifiers, adding differential privacy, and aggregating data across users - before ads are personalized and measured.

AEM covers two surfaces:

• Website events: measurement recovery for web conversion campaigns with iOS 14.5+ traffic.
• App events: sales, lead, and engagement campaigns with a mobile-app destination, later expanded to the app promotion objective.

What Changed: Meta Removed the AEM Configuration

Meta rolled out updates to website conversion campaigns that removed the configuration workflow entirely. According to the official help center:

• You no longer need to prioritize 8 conversion events per domain for web conversion optimization, and value sets are not required for value optimization.
• The Aggregated Event Measurement tab in Meta Events Manager has been removed because web events no longer need configuration.
• Domain verification is not required for purposes related to event configuration (it may still be needed for other reasons).
• You don't need to select a conversion domain when you create a campaign in Ads Manager.

The practical consequence: any guide that walks you through ranking 8 events per verified domain describes a removed interface. If your Events Manager has no AEM tab, that is the expected state, not a misconfiguration.

What AEM Still Does Today

Removing the configuration did not remove the protocol. AEM still processes web and app events from iOS 14+ devices with the same privacy protections, and Meta continues to evolve it. Two current behaviors matter for media buyers:

• MMP reporting: as of October 9, 2024, Meta sends AEM reporting to mobile measurement partners to give a more comprehensive view of user acquisition performance in MMP reporting surfaces.
• App campaign reporting and delivery: iOS 14+ campaigns that use AEM as the attribution method have access to 1-day click and 7-day click reporting for app event optimization and value optimization, plus delivery benefits such as longer 7-day click attribution windows and Audience Network delivery.

For website campaigns there is no per-domain event ranking to maintain, and no priority order that could suppress funnel events in aggregated reports.

Combining AEM with Conversions API (CAPI)

Server-side events via CAPI bypass browser restrictions such as ad blockers and ITP, and they remain the reliable way to deliver conversions from your own infrastructure. One official note matters for expectations: events sent to Meta via the Conversions API may also be processed in accordance with limits set by Aggregated Event Measurement. CAPI is not an opt-out from the protocol - it is a more reliable delivery channel into it.

What you still control is deduplication. Meta deduplicates events that arrive from both Pixel and CAPI within a 48-hour window when they share the same event_id, with the browser event taking precedence.

1. Keep your Pixel firing standard events in the browser.
2. Mirror the same events server-side through CAPI with matching event_id values.
3. Let deduplication collapse the double fire into one counted conversion.

For step-by-step CAPI integration with a tracker, read Facebook CAPI in Keitaro: Setup Guide. If you hit the 7-day event processing limit, see Facebook CAPI Error 2804003. The mechanics of shared identifiers are covered in event_id and Deduplication.

Browser Pixel  --->  event_id: abc123  --->  Meta receives both,
CAPI (server)  --->  event_id: abc123       counts once (deduplicated)

If you want automated routing that sends each conversion to the right platform without manual postback configuration, MOST handles conversion routing and reporting across ad networks. For a quick manual pixel activation without a tracker, Pixel Activator lets you fire test events directly.

Troubleshooting Web Conversion Reporting

After any change to your event delivery, use the Test Events tool to confirm events arrive correctly before judging aggregated reporting. The validation workflow is in Meta Test Events Tool: Validate Events.

Sources

domain verification for AEM priority.