What is App Tracking Transparency (ATT)?
App Tracking Transparency (ATT) is Apple's privacy framework, introduced in iOS 14.5, that requires apps to explicitly ask users for permission before tracking their activity across other companies' apps and websites. This primarily affects access to the IDFA (Identifier for Advertisers), the device-level identifier used for ad targeting and attribution.
When an app wants to track a user, it must present a system-level permission prompt. If the user chooses "Ask App Not to Track," the app cannot access the IDFA and must not engage in cross-app tracking. Industry-wide opt-in rates are approximately 25-30%, meaning the majority of iOS users are not trackable.
How it works
ATT operates at the OS level with a simple but impactful permission flow:
1. Permission request — The app calls the ATT framework to request tracking authorization. iOS displays a standardized prompt: "[App Name] would like permission to track you across apps and websites owned by other companies."
2. User decision — The user sees two options: "Ask App Not to Track" or "Allow." The app can add a single line of custom text explaining why tracking helps (e.g., "This helps us show you relevant ads").
3. IDFA access — If the user allows tracking, the app can access the IDFA for attribution and ad targeting. If denied, the IDFA returns all zeros (00000000-0000-0000-0000-000000000000).
4. System-wide setting — Users can also disable tracking globally in Settings > Privacy > Tracking, which blocks all apps from even showing the prompt.
Impact on attribution — Without IDFA, traditional deterministic attribution is impossible. The industry has shifted to SKAdNetwork for paid campaigns and probabilistic/fingerprint-based methods for organic attribution.
Why it matters
ATT has been the most significant change to the mobile advertising ecosystem in a decade:
- Reduced ad targeting accuracy — Without IDFA, personalized ad targeting is less precise on iOS - Attribution gaps — Marketers can't track individual user journeys across channels as easily - SKAdNetwork adoption — SKAN became the primary paid attribution method on iOS - Privacy-first solutions — Drove innovation in contextual targeting, on-device processing, and privacy-preserving measurement - Deep linking importance — Platforms like Redirectly that use deep link-based attribution (not IDFA) became more valuable as a privacy-compliant alternative
Frequently asked questions
How does ATT affect deep linking?
ATT does not directly affect deep linking. Universal Links, App Links, and deferred deep linking work independently of IDFA and ATT consent. However, ATT affects the attribution layer — knowing which campaign drove an install. Deep linking platforms like Redirectly use link-based attribution methods that don't require IDFA, making them ATT-compliant by design.
Should I still show the ATT prompt?
It depends on your monetization model. If you rely heavily on personalized advertising (especially with Meta or Google), showing the prompt and getting even 25% opt-in improves ad performance and attribution. If your app doesn't rely on ad-driven revenue, you may skip the prompt entirely — but you then cannot access IDFA at all.
Related terms
SKAdNetwork
Apple's privacy-preserving framework for measuring the effectiveness of advertising campaigns that drive app installs, without revealing user-level data.
Mobile Attribution
The process of identifying which marketing channel, campaign, or touchpoint led a user to install or engage with a mobile app.
Mobile Measurement Partner (MMP)
A third-party analytics company that helps app marketers measure and attribute installs and in-app events across advertising channels.