The Unique Device Identifier (UDID) is a 40-character hexadecimal sequence that distinguishes each individual iPhone. As an example, a UDID might resemble “e7c398cf47c7ca3aa87e2494897f1d976469b511.” Historically, this identifier served a crucial role in device identification for developers and mobile application testing.
The availability of a device’s distinct identifier allowed developers to provision beta versions of applications directly to specific hardware, bypassing the public app store. This facilitated targeted testing and ensured compatibility across a controlled set of devices. Furthermore, it enabled functionalities such as personalized application configurations and device-specific troubleshooting.