iOS ATT (App Tracking Transparency): Definition

What is iOS ATT?

DefinitionATT requires apps to ask permission before tracking, and most users decline - collapsing the signal ad platforms use for optimization and attribution since 2021. It’s the reason server-side tracking and modeled conversions now matter.

ATT shipped with iOS 14.5 in 2021 and turned cross-app tracking into an opt-in prompt most users decline, which is why Meta now models a meaningful share of iOS conversions instead of observing them. Health brands feel it more than most categories: telehealth and supplement traffic skews mobile, so a weight-loss advertiser sees fewer matched conversions, laggier reporting, and a platform CAC that reads worse than reality. The working response is to rebuild signal server-side: CAPI plus first-party data restores optimization signal without touching the health-data lines the FTC drew in its GoodRx and BetterHelp actions (2023).

iOS ATT (App Tracking Transparency)

What is iOS ATT?

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