Used by advertisers to serve personalised ads on iPhones and iPads, the Identifier for Advertisers (IDFA) is a unique, random identifier assigned to iOS mobile devices. The IDFA is anonymous, so it does not reveal any personal information, but it allows advertisers and app owners to identify specific mobile devices and collect information about their use, enabling customised, targeted ads to be displayed.
Following the introduction of Apple’s new App Tracking Transparency (ATT) framework (as part of its iOS 14 update), however, users must now be given the option – at the app level – to opt-out of sharing IDFA information. This is expected to reduce the reach of targeted advertising via the IDFA and will see advertisers focusing on other targeting methods, such as collecting first-party data.
The Android version of IDFA is the GPS ADID (Google Play Services ID for Android).