I want to use MAC address of the iphone as my unique identifier of the app. I was wondering if it changes or is it unique per device.
Thanks
Do not use the MAC address as a replacement for the UDID. Use the Identifier For Advertisers [IDFA] or the Identifier For Vendors [IDFV] instead.
p1. The MAC address is not required to be globally unique.
p2. Even when the U/L bit in the EUI-48 or EUI-64 format identifies the address as "universal," the MAC address is not required to be globally unique. All that bit really means is that the OUI is globally registered, and the organization that it identifies is assuming responsibility for registering the individual addresses that use that OUI.
p3. Seriously, the MAC address is not globally unique. Ask anybody who works in a network interoperability laboratory. Hardware manufacturers reuse them all the time, according to policies they never discuss publicly. It is not a replacement for the UDID.
p4. The operating system is under no obligation to present the actual hardware MAC address to non-privileged applications. The current version may be doing that today, but some future version might rather suddenly and silently stop doing that. It could start returning an identical address on every device.
Do not use the MAC address as a replacement for the UDID. Use the Identifier For Advertisers [IDFA] or the Identifier For Vendors [IDFV] instead.