Adding devices to your Apple Developer account allows you to select iOS devices to permit for testing an app locally. You will need:

iTunes Update

Ad-Hoc Testing is ONLY possible on versions of iTunes 12.6.2.20 and earlier. Click here to find your version.

To add a device to your Apple Developer account:

Open iTunes
Connect an iOS Device to your computer
Click the Device icon
Click Summary along the left-hand side
Under Phone Number click the cell. It will magically change to display the UUID!
Click on UUID and Copy
Login to Apple Developer
Click Certificates, Identifiers and Profiles
Click Devices and the +. Add Name and UUID that's copied on the clipboard.
Click Continue and Add Device

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