The UDID is a feature of Apple mobile devices and stands for Unique Device ID that is made up of a sequence of 24 to 40 characters. To get your device UDID, we recommend you to use this web-based tool: http://get.udid.io/.
Here's an alternative way to get your UDID:
- Connect your iPhone to your Mac.
- Open iTunes app from the Dock or 'Applications' folder on your Mac.
- Click the phone icon, and you'll see your device serial number displayed right below your phone number.
- Click on Serial Number so that it changes to display your UDID.