Since 2011, Apple has discouraged app developers from targeting ads based on a mobile device’s Universal Device Identifier (UDID). In its place, Apple has asked that developers rely on
Advertising IDs, which device owners can ostensibly turn off if they don’t want to be tracked by advertisers. Nick Arnott, an engineer at iPhone app consultancy Double Encore, explores the
policy and its impact on advertisers, developers, and users. Overall, he writes: “Apple’s move away from UDIDs is a good thing.”