Microsoft Authenticator is a free mobile app that provides secure two-factor authentication (2FA) for Microsoft accounts and thousands of other online services. It generates time-based one-time passcodes (TOTP) or sends push notifications for easy approval of sign-in requests. The app supports passwordless sign-in, enhancing security by allowing users to authenticate with biometrics or PIN instead of passwords. Available on Android and iOS, Microsoft Authenticator also supports multi-account management and integrates with Azure Active Directory for enterprise-level identity protection. It works offline for generating verification codes and helps protect accounts from unauthorized access and phishing attacks.