Why lowercase uuid?

Question

I’m considering using uuid to differentiate my swift app, and looked around online for how to achieve it. While searching, I often found people lowercase the uuid such as:

let uuid = NSUUID().UUIDString.lowercaseString

Wouldn’t lowercasing the uuid be unnecessary or make it less random?

Answer 1

It is not less random, because UUIDs are not case-sensitive. UUIDs are 128-bit numbers, and in string form they are represented using hexadecimal digits. ‘A’ and ‘a’ are the same digit.

Standards such as ITU-T X.667 and RFC 4122 require them to be formatted using lower-case letters, but also require parsers to accept upper-case letters.

The NSUUID class and UUID struct use upper-case letters when formatting. Long ago, someone either got it wrong, or made the decision before the choice of lower-case letters was standardized. Apple won't change it now because doing so could break existing code that relies on the use of upper-case letters.

On Apple platforms, the UUID formatting code, unparse.c, is written in C, and (according to the copyright) was originally written by Theodore T'so in 1996 or 1997. But the code uses upper-case letters because UUID_UNPARSE_DEFAULT_UPPER is defined in uuid-config.h.

Answer 2

Because it is required by international standards

You may find the information here

6.5.4 Software generating the hexadecimal representation of a UUID shall not use upper case letters. NOTE – It is recommended that the hexadecimal representation used in all human-readable formats be restricted to lower-case letters.