Unity & In-App UA
IDFA
Apple's per-device advertising identifier, available only when the user accepts the ATT prompt; the Android equivalent is GAID. Its decline is why in-app iGaming leans on SKAN, cohorts and modelled windows instead of device-level attribution.
IDFA is Apple's per-device advertising identifier. Since iOS 14 it is only available when a user accepts the ATT prompt, and most do not, so for the majority of iOS traffic the deterministic link between an ad click and that user's later behaviour is gone. The Android equivalent, GAID, has not been restricted in the same way, which is why Android and iOS reporting on the same campaign rarely look alike.
The consequence is not that iOS is unmeasurable but that it is measured differently: aggregated and delayed through SKAN, with modelled rather than observed events. Numbers arrive later and coarser, so decisions lean on cohorts and matured windows instead of same-day dashboards. Putting an iOS campaign and an Android one side by side on identical reporting is a measurement mistake before it is ever a performance conclusion.
In buyer speech
“Do not put iOS and Android in one sheet, one is SKAN-modelled and the other is real postbacks.”