# What is Aggregated Event Measurement (AEM)? > Aggregated Event Measurement is Meta's privacy method for counting iOS 14 and later conversions. What it is, what changed for web events and how to check your data. - **Author**: Marxx - **Published**: 2026-11-10 - **Category**: Measurement - **URL**: https://marxx.ai/library-glossary/aggregated-event-measurement --- Aggregated Event Measurement (AEM) is Meta's protocol for measuring web and app actions from people on iOS 14 and later devices. It counts conversions in groups, with privacy steps such as removing identifiers and adding differential privacy, instead of following single people ([Meta Help Center](https://www.facebook.com/business/help/721422165168355), checked 2026-10-20). ## What changed for web events AEM used to ask web advertisers to prioritise 8 conversion events per domain. Meta's help page now lists these changes for accounts that have the update (checked 2026-10-20): - You no longer prioritise 8 conversion events per domain. - You do not need value sets to use value optimisation. - The Aggregated Event Measurement tab in Events Manager is gone. - You do not need to verify your domain for event setup. You may still need it for other reasons. - You do not pick a conversion domain when you create a campaign. Meta adds that events sent through the [Conversions API](/glossary/conversions-api) may also be processed under AEM limits. ## Why it matters to you AEM gives limited measurement for iOS users, so Ads Manager can count fewer orders than your store does. That gap is normal. A sudden change in the gap is not. ## A worked example Say your store records 400 orders in a week. Ads Manager reports 310 purchases. **Reported share = Meta purchases / store orders x 100** 310 / 400 x 100 = **77.5%** Track this share every week. If it holds near 77%, Meta's numbers are a steady, partial view. If it falls to 50% in one week, check your Pixel and Conversions API setup before you blame the ads. See [Pixel vs Conversions API](/compare/pixel-vs-conversions-api). For why Meta and Google Analytics never match, read [GA4 vs Meta Ads Manager numbers](/compare/ga4-vs-meta-ads-manager-numbers). The days a sale can count for an ad also change the number. See [attribution window](/glossary/attribution-window). ## FAQ ### Do I still need to set up AEM for my website? For web events, Meta says there are no steps you need to take for events to be processed through AEM, once you have the update. App campaigns have their own eligibility checks on Meta's help pages. ### Is AEM the same as Apple's SKAdNetwork? No. AEM is Meta's protocol and SKAdNetwork is Apple's. For app campaigns, Meta says AEM and SKAdNetwork reporting may show differences ([Meta Help Center](https://www.facebook.com/business/help/3499572073626051), checked 2026-10-20). ### Does AEM change my ROAS? It can change what Meta reports, because Meta says AEM recovers only limited measurement of iOS website conversions. Check [ROAS](/glossary/roas) against your store data, not Ads Manager alone. --- - [More Measurement articles](https://marxx.ai/library-glossary/category/measurement) - [All articles](https://marxx.ai/library-glossary)