That's not quite right. If you turn it off apps may still be able to track you nefariously but they'll be violating Apple's policies.
Apple's explanation for wording it this way is that it's impossible to block all tracking through technical means at the system level because there will always be new nefarious tricks that malicious people will try to use against you. They can only do it at the policy level and try to punish bad actors.
But that’s a very different question. If you say yes, you get lots of pop ups from apps asking to track, and if you say no, they track you without asking.
It turns off the ask, so the way it works is you need to ask and then you need to wait for a response and if that response is "Yes" they can then begin tracking. In any other case/situation you are not able to.
So if you don't want this asking you everytime you open any app (based on my experience it happens frequently) you can turn it off.
It would ask once per app, per install. This global setting just auto denies it for every that asks, and I'm pretty sure ( but haven't tested ) retroactively denies any app you had previously said yes to.
Source: I'm a newly role changed iOS developer at my job.
From a Wall Street Journal interview with Apple's Craig Federighi:
WSJ: "Why the verbiage 'Ask Not to Track'? Why not just 'Do Not Track'?"
Federighi: "There are other techniques that developers over time have developed, like fingerprinting, which is a bit of a cat and mouse game around other ways that an app might scheme to create a tracking identifier. And it's a policy issue for us to say 'you must not do that'. And so, we can't ensure at the system level that they're not tracking, [but] we can do so at a policy level."
Agree that it seems weird, and that it doesn't align with their other permissions wording: "always allow without prompting", "allow each app to ask once", "always deny without prompting".
That’s the setting in iOS under Settings > Privacy > Tracking.
What does it actually mean?
If it’s turned off, does that means that apps are tracking you since they don’t have to ask?
If it’s turned on, does that mean apps have to ask and you can disable tracking per app?
Something feels very strange about the way this setting is worded. I’d have excepted something like: “Allow Apps to Track” [ On | Off ]