Udid is unique device identifier for apple devices. ios developer use this device identifier to identify a particular device. but for a normal device user it’s an unfamiliar word and incase they want to get it there are different ways.
we are using iTunes here.
Step 1: Open up iTunes in your Mac. you can search for iTunes in your Mac.
Step 2: connect your device through usb cable to your Mac.if connected properly device icon will be shown in iTunes header section.
click on it to see device details.
Step 3:there in device information section you will see device information like serial number etc. click there and you will also find udid there.
Step 4:if all the steps followed properly udid will be displayed.