App Tracking Transparency (ATT)
App Tracking Transparency is an iOS framework requiring apps to ask user permission before tracking activity across other apps and websites for advertising purposes.
Introduced in iOS 14.5 (April 2021), ATT changed iPhone advertising overnight. Before ATT, apps could read the IDFA — a stable advertising identifier — by default. After ATT, the IDFA is gated behind a system prompt: "Allow X to track your activity across other companies’ apps and websites?" Roughly 75–85% of users decline, depending on the app.
When the user declines, the app gets a zeroed IDFA and must rely on Apple’s privacy-preserving SKAdNetwork for marketing attribution. That works at the campaign level (which ad campaign drove this install?) but not at the user level (which user installed and converted?).
ATT is one of three iOS privacy labels (alongside Privacy Manifest and the Privacy Nutrition Label) that together tell App Store reviewers, regulators, and users what data an app collects, why, and from whom.
Summio asks for ATT permission once. If you decline, the app works fully — only attribution measurement is limited. Marketing partners receive only privacy-preserving SKAdNetwork postbacks; we never access your IDFA without your consent.
Read more about Summio →Common questions
What happens if I tap "Ask App Not to Track"?
The app cannot read your IDFA. It will still work normally — only its ability to measure advertising is reduced. Apps that block functionality based on the ATT response violate Apple’s App Store guidelines.
Is ATT the same as Apple’s Privacy Nutrition Label?
No. The Privacy Nutrition Label is a static disclosure on the App Store listing about what data the app collects. ATT is a runtime prompt about cross-app tracking specifically. An app can disclose data collection on its label and still be obligated to ask via ATT.
Can I change my ATT decision later?
Yes — iOS Settings → Privacy & Security → Tracking. You can toggle individual apps on or off there, or disable cross-app tracking globally for all apps.