How to get Unique Device Identifier (UDID) on the iPhone
UDID stands for Unique Device ID, it's a Unique number of each Apple devices that is made up of a sequence of 40 letters and numbers.
Why we need UDID number?
We all are aware of security in Apple Devices. Apple only allow users to install applications that are approved by Apple and are in the App Store. iOS App Development requires that apps submitted to the App Store are compliant with their standards. So, after development if you want to test the iPhone app, we need to register a device for an Apple developer account with the unique UDID
How To Find Your UDID?
For an Apple developer to register a device for testing, you need to first find its UDID.
1. Launch iTunes & connect your iPhone, iPad or iPod (device).
2. Under Devices, click on your device
3. Next click on the ‘Serial Number’
4. This should change the Serial Number into the UDID
5. Choose ‘Edit’ and then ‘Copy’ from the iTunes menu.