The Unique Device Identifier is a 40-character alphanumeric that works as a device-identifying mechanism. It's an ID that uniquely identifies your iPhone. If you're not a developer working on iOS apps (a.k.a the average John Doe like us), you're most likely not going to need it ever.
But just in case you want to find your iPhone's UDID, here's how to do that:
- Connect your iPhone to the computer.
- Fire up iTunes.
- Click on your device's name on the sidebar (in iTunes 11, enable the sidebar from the View menu option.)
- Now you're on the summary tab. Do you see that ‘Serial Number'? Wait, that's not it.
- Click on the Serial number and pop! Here's the UDID.
- If you hit Ctrl+C (Command+C in Mac), this UDID number gets copied.
RELATED: How to Find Mac UUID
As a normal user, we're mostly never going to need (or worry about) UDID. This UDID actually helps Apple recognize your device and although it does slightly sound like Apple's peeping into your device, it's not like that. UDID is most specifically useful for Apple to identify developers who are testing stuff on their iPhones. Like, say, apps. Well, apps is the only thing devs could be testing in conformation with Apple's policies.
For developers, the UDID was readily available via the UIDevices class. Till iOS 6 came up, when Apple decided to end that thing. Obviously, this was for security reasons.
If you're a novice developer looking to figure out how to use UDID, I think the answer is “you can't.” While the above method of ‘finding' the UDID of your iPhone (or any iDevice in your hand right now) works just fine, for code purposes – where you want to figure out the UDID or use it – that ain't gonna fly.
You might have to resort to using other options like OpenUDID.
Note that using any ID to track is a touchy area right now unless you're doing it for a really transparent reason that's so boring that no one bothers.
Also note that the UDID is completely different from the Advertising Identifier and these are not related at all.