Identifier for Advertisers (IDFA)

What is IDFA

The IDFA is a unique string of numbers and letters that allows advertisers to identify individual iOS devices without revealing personal information. It is user-resettable, meaning users can reset it at any time if they want to limit tracking.

For advertisers and affiliate marketers, IDFA is a key tool for:

• Measuring app installs and campaign conversions

• Tracking user interactions across multiple apps

• Understanding the effectiveness of advertising campaigns

By connecting ad impressions to user actions, IDFA helps marketers optimize campaigns and allocate budgets more efficiently.

IDFA and App Tracking Transparency

With the introduction of Apple’s App Tracking Transparency (ATT) framework, access to the IDFA is no longer automatic. Apps must request explicit permission from users before they can access this identifier.

• If a user grants consent, the app can use the IDFA for tracking and attribution.

• If a user denies consent, the IDFA becomes unavailable and returns a zeroed value.

• Users can reset or revoke access to IDFA at any time via their device settings.

This shift has significantly affected how advertisers measure performance on iOS, requiring new strategies to maintain visibility into user behavior while respecting privacy.

Why IDFA matters

IDFA plays an important role in accurate attribution, audience measurement, and campaign optimization on iOS. For affiliate marketers and advertisers, IDFA opt-in rates directly impact the ability to track performance and optimize user acquisition. As ATT has reduced IDFA availability, many teams now rely on a mix of IDFA-based tracking, privacy-first attribution solutions like SKAdNetwork, and first-party data to maintain visibility into campaign results.