iPhone UDID using iTunes

How to find iPhone UDID (Unique Device Identifier using iTunes)

Plug your phone in to your PC/laptop and start iTunes software.

Click on phone icon highlighted in image below, don’t click the eject button

Another UI screen will be shown as a result of this click, the UI screen looks like following:

Only after a single click, the text label will start displaying the UDID of the phone which is needed for enabling testing on tester devices. 

Right click the cryptic looking alpha-numeric string and select copy. Please note that I have distorted the UDID intentionally.

Now you can paste it anywhere and email me, or even get it tattooed on the biceps.

What is a UDID?

The iOS device UDID is added to a provisioning profile, it allows ad-hoc deployment of your apps during testing to the iOS devices of your testers. You would've already guessed that its a unique identifier and no other Apple mobile device will have this identifier on it.

Please note that only 100 iOS devices be it iPhone/iPod/iPad can be added to a single Apple Developer Account.

In case of Android, you can create a development build and send the apk file to any number of people who may deploy it on any number of devices.