usernameConfiguration

Case sensitivity of the username input for the selected sign-in option. When case sensitivity is set to False (case insensitive), users can sign in with any combination of capital and lowercase letters. For example, username, USERNAME, or UserName, or for email, email@example.com or EMaiL@eXamplE.Com. For most use cases, set case sensitivity to False (case insensitive) as a best practice. When usernames and email addresses are case insensitive, Amazon Cognito treats any variation in case as the same user, and prevents a case variation from being assigned to the same attribute for a different user.