What is proper username in Cognito User Pool?

Question

I need to check that a proper username is entered in the custom signin form on my web site to pass it to Auth.signUp method of aws-amplify.

Things like minimum/maximum number of characters and allowed characters.

Documentation at this link does not help, please point me to a correct page, thank you!

Answer 1

See AWS SDK for validation rules.

The username for the user. Must be unique within the user pool. Must be a UTF-8 string between 1 and 128 characters . After the user is created, the username can't be changed.

https://docs.aws.amazon.com/AWSJavaScriptSDK/v3/latest/clients/client-cognito-identity-provider/interfaces/admincreateusercommandinput.html

Not perhaps a perfect description but has at least the minimum and maximum character count.

Edit: Cognito API reference reveals that regex pattern for username validation is: [\p{L}\p{M}\p{S}\p{N}\p{P}]+

https://docs.aws.amazon.com/cognito-user-identity-pools/latest/APIReference/API_AdminCreateUser.html

BTW, username cannot be changed after creation so perhaps you want to use preferred_username attribute to store the username which a user submits in sign in form (and make back-end to generate a value for username automatically (uuid for example)).

The document behind the link states:

Activate the preferred_username attribute so that your user can change the user name that they use to sign in while their username attribute value doesn't change.