The documentation is clear about what not to use for the Custom App User ID.
What is recommended to create a Custom App User ID?
My app is written in Flutter/Dart.
Thanks,
Userlevel 4
+6
Hey
Generally, we recommend using a database identifier for your users that you might have from your own authentication system. If you don't have a login system for your app, I'd recommend not providing any App User ID - in that case, RevenueCat will generate an anonymous identifier for the user and handle it automatically.
You can read more about identifying users in our docs here: https://www.revenuecat.com/docs/user-ids#anonymous-app-user-ids
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