User authentication is a critical security aspect in web applications. Best practices include using secure password hashing algorithms like bcrypt or Argon2, which are designed to be computationally expensive and mitigate brute-force attacks. Implementing multi-factor authentication (MFA) adds an additional security layer beyond passwords. Securely managing session tokens, such as using HTTPS and setting appropriate cookie attributes, prevents token hijacking. Libraries like Flask-Security and Django’s built-in authentication system provide robust authentication mechanisms.