As an iOS application developer, there will be times when you need to try out your apps on one or more test devices before submitting it to Apple for the App Store approval process. In cases where these devices are your own, you can always set up the device for development and use Xcode to debug applications on the device. In many cases, however, these devices may not be physically accessible; for example, if a client asked you to provide a preview of your app for them to try out on their devices. In these cases you will need to prepare your app for Ad Hoc distribution.
Using Ad Hoc distribution, you can distribute your application to a limited number of devices outside the App Store. The standard iOS developer account enables you to specify up to 100 devices each year, which can be used for development or Ad Hoc distribution. It is important to remember that Ad Hoc distribution is not a replacement for App Store distribution. Apps that are distributed in this manner will eventually expire, at which point they can’t be run on the test devices.
Each iOS device has a unique 40-digit identifier, commonly referred to as the device UDID. Before you can use Ad Hoc distribution for your apps, you must obtain and register the UDIDs of each device with the iOS Provisioning Portal.
You can obtain the UDID with Xcode or iTunes. To obtain the UDID for a device with iTunes, simply connect the device to a computer with iTunes installed ...