4D v12 uses the following APIs for UUID generation:

UuidCreate on Windows:

https://msdn.microsoft.com/en-us/library/aa379205(VS.85).aspx

CFUUIDRef on Mac:

https://developer.apple.com/mac/library/DOCUMENTATION/CoreFoundation/Reference/CFUUIDRef/Reference/reference.html

More information about the different versions of UUIDs can be found here:

https://en.wikipedia.org/wiki/Universally_Unique_Identifier

Please note that this information is subject to change and was correct at the time of publishing this Tech Tip.