Normally the simplest way to get the UDID is to use iTunes, when the device is connected using the USB cable, to read the value. Sometimes, especially when you are away from your desktop, it may be more convenient to download a small utility from the App Store.

USING ITUNES

1. Open iTunes and connect your device using the USB cable.
2. In the source list, on the left, select your device.
3. In the main panel, show the device's information by selecting the tab labelled Summary
4. Reveal the identifier by clicking the label text Serial Number
5. Copy the value to the pasteboard by selecting the Copy item from the Edit menu.

USING A FREE HELPER APP

There are a number of general purpose UDID utility apps in the Store, try searching for UDID, but we have found Ad Hoc Helper to be simple to use and reliable. There is yet one more great free App in the App store called UDID Tool.