>When we select “Ask App Not to Track,” two things happen. The first is that Apple disables the app from using an Apple device identifier, a random string of le

>When we select “Ask App Not to Track,” two things happen. The first is that Apple disables the app from using an Apple device identifier, a random string of letters and numbers that is assigned to our iPhones and is used to track our activities across apps and websites. The second is that we communicate to the app developer that, broadly speaking, we don’t want our information to be tracked and shared with anyone in any way. >That seems easy enough. But No. 2 is where things also get slightly complicated. >Ad-tech companies already have many ways to follow us beyond Apple’s device identifier. For example, advertisers can use a method called fingerprinting. This involves looking at seemingly innocuous characteristics of your device — like the screen resolution, operating system version and model — and combining them to determine your identity and track you across different apps. How effective this all is will completely rely on how Apple reacts to the first app it catches breaking the rules.