AuthenticatorApp

An authenticator app is a software application used to perform multi-factor authentication by generating or delivering a second factor during login. These apps run on smartphones or computers and are used with online services that support MFA, providing an additional barrier beyond a username and password.

Most authenticator apps implement time-based one-time passwords (TOTP) or event-based one-time passwords (HOTP). During setup, the service provides a shared secret (often via a QR code) that the app stores securely. When logging in, the app computes a short numeric code based on the secret and the current time (for TOTP) or a counter (for HOTP). The code expires after a short window, typically 30 seconds. Some services also offer push-based authentication, which sends a prompt to the app for automatic approval on the registered device.

Provisioning typically involves importing or adding multiple accounts within the app. Codes can be generated offline, but many apps offer cloud backup or encrypted synchronization so accounts survive device loss. Codes are device-specific and are not transmitted to the service during login beyond the code entry itself. The approach is widely supported by major identity providers and 2FA workflows.

Security considerations include the risk that a compromised device could disclose codes, and the need to protect the app with a device lock or biometric authentication. Users should enable backup protections, disable screen sharing, and secure recovery options such as backup codes. Authenticator apps do not guard against phishing by themselves; some phishing-resistant MFA methods complement them.

Examples of authenticator apps include Google Authenticator, Microsoft Authenticator, Authy, LastPass Authenticator, Duo Security, and 1Password's built-in TOTP generator. The concept emerged in the early 2010s as part of broader MFA adoption and remains a common, portable method for second-factor authentication.