What is a UDID?
UDID stands for Unique Device Identifier, it is most commonly used by developers but is also used to review and test iOS applications. UDID is a unique identifier for the iOS device. Much can be done with UDID by the developers testing apps in beta mode by specifying permissions to keep their apps a secret until released to the public.
It is very easy to locate the device’s UDID. Follow these steps below to get our UDID.
Connect your iOS device to a computer
You will need iTunes running on the computer where you’ll be connecting the the device. Most people already sync their iPad’s / iPhones with their computers running iTunes. If you do not have iTunes, then you need to get one from http://www.apple.com/itunes/ and install it.
Now connect the device to the computer, and launch iTunes. It opens up automatically though.
Get to the information screen for the device, this is located above the left pane (upper left) indicated by a device icon. Once you click it, it will show you the device information.
Now locate the serial number, as indicated by the arrow in image below
Now start clicking the serial number until you see UDID. Additional clicks on the serial number may produce other data, so if you see something else other the UDID, then keep hitting it until you see UDID.
The serial number cannot be highlighted, and it is a large number. So what you can do is either write it down, or right click and select copy.