Version: 2017.3

SystemInfo.deviceUniqueIdentifier

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public static string deviceUniqueIdentifier ;

Description

A unique device identifier. It is guaranteed to be unique for every device (Read Only).

iOS: on pre-iOS7 devices it will return hash of MAC address. On iOS7 devices it will be UIDevice identifierForVendor or, if that fails for any reason, ASIdentifierManager advertisingIdentifier.

Windows Store Apps: uses AdvertisingManager::AdvertisingId for returning unique device identifier, if option in 'PC Settings -> Privacy -> Let apps use my advertising ID for experiences across apps (turning this off will reset your ID)' is disabled, Unity will fallback to HardwareIdentification::GetPackageSpecificToken().Id.

Windows Standalone: returns a hash from the concatenation of strings taken from Computer System Hardware Classes (https://msdn.microsoft.com/en-us/library/windows/desktop/aa389273(v=vs.85).aspx):
Win32_BaseBoard::SerialNumber
Win32_BIOS::SerialNumber
Win32_Processor::UniqueId
Win32_DiskDrive::SerialNumber
Win32_OperatingSystem::SerialNumber

Will return SystemInfo.unsupportedIdentifier on platforms which don't support this property.