UDID (Unique Device Identifier) is a unique alphanumeric code assigned to each iOS device. In the context of Ad Hoc provisioning profiles for iOS apps, UDIDs are used to specify the devices on which the app can be installed and tested outside of the App Store. By including the UDIDs of specific devices in the Ad Hoc provisioning profile, you restrict the installation and execution of the app to those devices only. This allows you to distribute the app to a limited group of testers for testing purposes without submitting it to the App Store. Collect UDIDs To distribute your app for Ad Hoc testing, you need to obtain the UDIDs of the devices on which you want to install and test the app. The UDID can be obtained by connecting the device to a computer with iTunes or by using third-party tools or services. Add UDIDs to the Apple Developer Account In the 'Devices" section of your Apple Developer Account, you will have the option to add the devices (identified by their UDIDs) that will be included in the AdHoc Provisioning profile of your future test app.