Many web applications require users to sign in and out in order to perform important tasks (like administration duties). In this article, we’ll create an authentication system for our application. In the previous article, we built a contact page using the Flask-WTF and Flask-Mail extensions. We’ll use Flask-WTF, once again, this time to validate a user’s username and password. We’ll save these credentials into a database using yet another extension called Flask-SQLAlchemy.