Apple’s world doesn’t have cookies. It has an equivalent called Identifier for Advertisers (IDFA).
From Adjust: “The IDFA is a random device identifier assigned by Apple to a user’s device. Advertisers use this to track data so they can deliver customized advertising. The IDFA is used for tracking and identifying a user (without revealing personal information). The data can then be used to discover information such as which in-app events a user triggers. The IDFA can also identify when users interact with a mobile advertising campaign, provided the channel offers IDFA tracking and the advertiser tracks users who interact with as successfully. If this occurs, the IDFA can identify whether specific users click an advert for payment and attribution purposes.”
More from Mozilla’s blog: “IDFA…is a random identification number, similar to a cookie, that tracks what you do in apps on your device. Each iPhone comes equipped with its own unique ID attached, which allows advertisers to track your interactions from what you click on, to what apps you install, to what videos you watch. The New York Times did an investigation last year that found data brokers were able to link these IDs with other information like name, location or email address to make complex user profiles, which isn’t great for your privacy. If you have an iPhone and didn’t turn this identifier off, then yes. It was possible to turn it off before, but you had to manually go in and do it yourself. Almost 70% of people did not turn off the tracker, according to a 2020 study by the analytics platform, Singular.”
Invoca: “You can think of an IDFA as something like a cookie that is tied to devices instead of browsers, in that it enables an advertiser to get notified when a user of a phone has taken an action like clicking on their ad in a browser and then installing, using, or interacting with ads in their app. This identifier is used in non-browser apps, which never had support for cookies. IDFAs only provide advertisers data in aggregate and no individually identifiable data is available.”
Cookies and IDFA are the trackers that power the world of digital advertising. And then in one fell swoop, Google decided to do away with third-party cookies and Apple made big changes to IDFA.