App tracking transparency (ATT)

What is App tracking transparency (ATT)?

App Tracking Transparency (ATT) is a privacy framework introduced by Apple in iOS 14.5 that requires apps to obtain explicit user permission before accessing the IDFA (Identifier for Advertising) and tracking user activity across apps and websites owned by other companies. ATT mandates that apps display a standardized system prompt asking users to allow or deny tracking. Apps that do not receive user permission are prohibited from using the IDFA for cross-app tracking or sharing data with third-party advertisers for targeting purposes.

How it works

When an app requests tracking permission under ATT, iOS displays a system-level prompt that asks the user whether to 'Allow Tracking' or 'Ask App Not to Track'. The app developer may also display a custom pre-prompt message to provide context before the system dialog appears.

Permission States

ATT returns one of four authorization statuses for each app: authorized (user granted permission), denied (user explicitly declined), restricted (tracking is restricted at the device level, such as for child accounts), or notDetermined (the permission request has not yet been shown). Only the authorized state grants access to the IDFA.

IDFA Access and Attribution Impact

Before iOS 14.5, apps could access the IDFA freely unless the user had manually enabled Limit Ad Tracking (LAT). After ATT, the IDFA is zeroed out (returned as all zeros) for any app that does not hold user permission. This fundamentally changes how mobile measurement partners and ad networks attribute installs and in-app events. When IDFA is unavailable, measurement must rely on privacy-preserving alternatives such as SKAdNetwork (SKAN), probabilistic modeling, or aggregated signals.

App Store Privacy Labels

Alongside ATT, Apple introduced App Store privacy nutrition labels. Developers must disclose their data collection and data-linked-to-user practices in the App Store listing before users download the app. This gives users visibility into tracking practices before installation.

Why it matters

ATT fundamentally reshaped the iOS mobile marketing ecosystem. The inability to access IDFA without consent reduces the granularity of user-level attribution data available to advertisers and mobile measurement partners. Campaigns that previously relied on deterministic IDFA-based attribution must now operate with a combination of consented user data and privacy-preserving measurement frameworks like SKAdNetwork. This affects retargeting, lookalike audience building, and the precision of cost-per-install and return-on-ad-spend calculations. For app developers, the quality of the pre-permission prompt and the context in which it is shown directly influences opt-in rates, making the permission request a meaningful part of the user acquisition strategy. Airbridge supports ATT-aware attribution workflows, including SKAdNetwork integration and probabilistic modeling for users who decline tracking, enabling advertisers to maintain measurement coverage across both consented and non-consented iOS users.

How to implement App Tracking Transparency in your iOS app

1. Add the NSUserTrackingUsageDescription key to your app's Info.plist file. The string value should clearly explain why your app requests tracking permission, as Apple reviews this for App Store compliance.

2. Import the AppTrackingTransparency framework and call ATTrackingManager.requestTrackingAuthorization(completionHandler:) at an appropriate point in the user journey, typically after onboarding or at a moment of high user engagement to maximize opt-in rates.

3. Display a custom pre-prompt (optional but recommended) before triggering the system dialog. This allows you to explain the value exchange, such as informing users that allowing tracking enables more relevant ads or supports free content.

4. Handle all four authorization states in your completion handler. Only proceed with IDFA-based tracking when the status is .authorized. For all other states, route attribution through SKAdNetwork or probabilistic modeling.

5. Integrate with a mobile measurement partner such as Airbridge to ensure that attribution events are captured correctly regardless of ATT status. Airbridge routes iOS attribution through SKAdNetwork for non-consented users and deterministic attribution for consented users, providing a unified view of campaign performance.

6. Review your App Store Connect privacy labels to ensure your declared data collection practices accurately reflect your ATT implementation. Mismatches can result in App Store rejection or removal.

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