App Tracking Transparency (ATT)
ATT is Apple's iOS framework requiring apps to get explicit user permission before tracking activity across other companies' apps and sites.
Definition
App Tracking Transparency (ATT) is an iOS 14.5+ framework that requires every app to display a standardized permission prompt before accessing a device's IDFA (Identifier for Advertisers) or tracking users across apps and websites. Without the user's explicit opt-in, apps cannot perform user-level cross-app attribution or share data with third-party measurement tools at an individual level.
The industry-wide opt-in rate for ATT prompts has settled at 25–45% depending on app category, meaning 55–75% of iOS users cannot be tracked at the user level for attribution purposes. This fundamentally changed iOS UA by reducing the data available for targeting, attribution, and audience building.
For UA teams, ATT means a significant portion of iOS campaigns are measured through SKAN's aggregate signals rather than user-level MMP data. The combination of SKAN-attributed installs and modeled conversions (from Meta's Conversions API) is now the standard iOS measurement approach.
Why it matters
ATT is the single biggest structural change to mobile advertising measurement in the last decade. Teams that don't understand ATT opt-in mechanics and SKAN fallback attribution will systematically misread iOS campaign performance, over-attributing success to opted-in users and under-counting conversions from the majority who opted out.
Frequently asked questions
Can you improve ATT opt-in rates?
Yes. Showing a pre-permission prompt explaining why tracking benefits the user (better ads, free content support) before the mandatory Apple prompt can significantly improve opt-in rates. Timing matters too, prompting after users have experienced app value converts better than prompting at first launch.