apple sign in : how is calculated the user id?

Question

How is calculated the value of the user id that returns the apple sign in? it looks like 000011.9134c48e58484ad52299cb393541aa78.1781. Is it a totally random number? Is this number unique per app?

Answer 1

Apple has not provided any information on how the user identifier is calculated. Given that it is guaranteed to be unique across millions of users it can't be purely random. However, there is probably some randomness in its calculation.

Apple states

The user identifier has the following characteristics:

• Consists of a unique, stable string, and is intended for use as the primary identifier of the user.

• Uses the same identifier across all of the apps in the development team associated with your Apple Developer account.

• Differs for the same user across different development teams, and can’t be used to identify a user across development teams.

• Doesn’t change if the user stops using Sign in with Apple with your app, and later starts using it again.