ATTApp Tracking Transparency
ATT is Apple's iOS opt-in framework: apps must ask permission before tracking users across other apps and websites.
What does ATT actually mean?
App Tracking Transparency (ATT) is Apple's iOS opt-in framework, introduced in iOS 14.5 (April 2021). Apps that want to track users across other apps and websites must show a system prompt asking permission. The opt-in rate has stabilized around 20-30% globally.
ATT broke last-click attribution for mobile UA on iOS. Pre-ATT, Meta and TikTok could attribute installs and conversions back to specific ads via Apple's IDFA. Post-ATT, attribution on iOS depends on SKAdNetwork (Apple's privacy-preserving framework) plus probabilistic modeling. Reported ROAS on iOS dropped 30-50% overnight in mid-2021.
The industry response: server-side tracking via CAPI, mobile measurement partners (MMPs) for app attribution, and broader adoption of incrementality testing and MMM to estimate true performance independent of platform attribution.
Example
A user opens a fintech app on iOS. The app shows the ATT prompt asking permission to track. The user taps ‘Ask App Not to Track.’ Meta cannot now attribute this user's subsequent install to a previous ad click via IDFA.
When it matters
ATT is the foundational privacy event that broke iOS attribution. Modern UA strategy requires SKAdNetwork, MMP integration, and incrementality testing.
Related terms
SKAdNetwork
SKAdNetwork is Apple's privacy-preserving framework for mobile attribution. It provides aggregated, delayed conversion data without exposing user IDs.
MMP
An MMP is a third-party tool (AppsFlyer, Adjust, Singular, Branch) that handles mobile app attribution across ad networks, including SKAN and probabilistic modeling.
CAPI
CAPI sends conversion events directly from your server to the ad platform, bypassing browser-side limitations of pixel tracking.
Incrementality
Incrementality measures the additional revenue ads generate vs. what would have happened without them, usually measured via holdout tests or geo-experiments.
Find out which ads actually win.
advrt builds ads around your real product photos, tests them live on Meta and judges each one against your own account. Free plan, no credit card.