What is IDFA?
The Identifier for Advertisers (IDFA) is a unique, resettable identifier assigned to each iOS device by Apple. It allows advertisers and ad networks to track user activity across apps for attribution, targeting, and measurement purposes.
Since iOS 14.5, apps must request user permission through Apple's App Tracking Transparency (ATT) framework before accessing the IDFA.
IDFA Format
The ATT Revolution
Apple's App Tracking Transparency (ATT) framework, introduced with iOS 14.5 in April 2021, fundamentally changed mobile advertising:
Key Change
Before ATT, IDFA was available by default. Now apps must explicitly ask permission, and most users decline (~65-75% opt-out rates globally).
ATT Opt-In Rates by Category
| App Category | Average Opt-In | Top Performers |
|---|---|---|
| Gaming | 20% - 30% | 35% - 45% |
| Social Media | 15% - 25% | 30% - 40% |
| E-commerce | 25% - 35% | 40% - 50% |
| Finance | 30% - 40% | 45% - 55% |
| News/Entertainment | 20% - 30% | 35% - 45% |
| Utilities | 25% - 35% | 40% - 50% |
Impact on Mobile Advertising
- Attribution Challenges: Without IDFA, deterministic attribution becomes probabilistic
- Targeting Limitations: Cross-app retargeting and lookalike audiences are less effective
- Measurement Gaps: SKAN provides limited conversion data compared to IDFA-based attribution
- CPI Increases: Reduced targeting precision has raised user acquisition costs 15-30%
- Creative Importance: Contextual and creative-based strategies have become more crucial
Maximizing ATT Opt-In
- Pre-Permission Prompt: Explain value before showing Apple's ATT dialog
- Timing Matters: Ask after users experience app value, not at first launch
- Clear Value Exchange: Explain how tracking benefits the user experience
- Custom Copy: Use the usage description string to communicate your message
- Test Approaches: A/B test different pre-prompts and timing
Pro Tip: SKAN Integration
For users who don't opt-in, rely on SKAdNetwork (SKAN) for attribution. While limited, proper SKAN implementation ensures you still get campaign-level insights.
IDFA vs GAID
Android's equivalent is the Google Advertising ID (GAID). Key differences:
- GAID is still available by default on Android (though changing)
- Android users can opt-out via settings, but adoption is lower
- Google is moving toward Privacy Sandbox with similar restrictions planned