When you start testing an app in development, developers might ask for the UDID (Unique Device Identifier) of your iPhone or iPad. Here’s how to get your iPhone or iPad’s UDID:
Step 1: Open iTunes and connect the device to your computer.
Step 2: Select your device from the left side panel in iTunes.
Step 3: You should be on the Summary tab. Click on the text that says “Serial Number” and the text will change to say “Identifier (UDID)”. Your UDID is a string of numbers and letters that looks something like this: 91b5amt92a7e7c4b3329665af1bcp31ba4d9b412
Note: The serial number is not the same as your UDID.
Step 4: Now that you see your UDID number, click on it and press Command/⌘ + C (on a Mac) or CTRL+C (on a PC) to copy the number to your clipboard. Alternatively, you can also copy the number by clicking on it and then clicking Edit ➞ Copy.
That’s it. Now you just need to paste that number into an email and send it to your app developer. They’ll take care of the rest, and you’ll be testing your new iOS app in no time!