Identifier for Advertisers (IFA)

IDFA replaces and circumvents UDID's security and privacy issues. IDFA is a like a typical, yet random, serial number that is assigned to each iOS-powered device. Unlike UDID, IDFA is non-permanent and may be activated or deactivated by the user. Based on the user’s activity, the IDFA is sent to the advertising server, which, in turn, displays relevant ads. However, unlike UDID, IDFA does not identify the device or user. Rather, it groups different users by similar search or browsing activity for relevant and targeted advertising.