What is App Tracking Transparency (ATT)?

App Tracking Transparency (ATT) is Apple’s privacy framework that requires apps to ask users for permission before tracking them across other apps and websites.

If a user says “no,” you can’t access their Identifier for Advertisers (IDFA), which was a common way to link ad clicks to installs or conversions.

It was introduced in iOS 14.5 and completely changed how mobile attribution works.

How does it work?

When a user opens an app for the first time, iOS can trigger a system-level prompt:

"Allow [App Name] to track your activity across other companies’ apps and websites?"

If the user opts in, the app can access the IDFA for deterministic attribution and retargeting.

If the user opts out (which most users do), the IDFA returns as zeroed out, and traditional tracking breaks.

This impacts:

• Ad networks (can’t match clicks to users)

• Retargeting and lookalike audiences

• ROAS and LTV modeling

• Cross-app measurement and frequency capping

To comply with ATT, apps must use Apple’s native API and disclose how data is used in their privacy nutrition labels.

Why it matters

ATT fundamentally shifted the mobile marketing landscape from user-level tracking to aggregated, privacy-safe measurement.

It forced advertisers to adopt privacy-first solutions like SKAdNetwork, which doesn’t rely on IDFA but uses delayed and aggregated postbacks.

Understanding ATT is essential for any team working on growth, attribution, or monetization on iOS. It sets the rules of the game.

Ignoring ATT means blind spots in data, poor optimization, and compliance risks. Embracing it means adapting to new tools, modeling techniques, and focusing more on creative and product quality.