username

The value that you want to set as the username sign-in attribute. The following conditions apply to the username parameter.

• The username can't be a duplicate of another username in the same user pool.

• You can't change the value of a username after you create it.

• You can only provide a value if usernames are a valid sign-in attribute for your user pool. If your user pool only supports phone numbers or email addresses as sign-in attributes, Amazon Cognito automatically generates a username value. For more information, see Customizing sign-in attributes .