What would be the options available in a managed environment? I'm making a 3rd-party app which would be installed by end users who have iPhones managed by my customer through an MDM. I need to be able to uniquely identify the device across three systems: the MDM of customer's choice, my web API (which pulls data from the MDM) and my mobile app (which will connect to the web API). In the end I need to know that the device running the mobile app is the same device that my web API synced from the MDM. Ideally the unique ID should be read-only so that the MDM cannot override it. If using the serial number is out of the question, I imagine the solution would be the MDM pushing some data to my app? I found this old sample, but I don't know how relevant it is nowadays. https://developer.apple.com/library/archive/samplecode/sc2279/Introduction/Intro.html