Simple to use, fast, and with zero dependencies\*. The Browser One Time Password library is fully compliant with [HOTP](http://tools.ietf.org/html/rfc4226) (counter based one time passwords) and [TOTP](http://tools.ietf.org/html/rfc6238) (time based one time passwords).
\* requires [forge](https://github.com/digitalbazaar/forge) for window.sha1Hmac shim in older browsers and [es6-promise](https://github.com/jakearchibald/es6-promise) for ancient browsers.
It can be used in conjunction with the [Authy](https://www.authy.com/personal/), [Google Authenticator](https://github.com/google/google-authenticator/), and [Microsoft Authenticator](https://www.microsoft.com/en-us/store/apps/authenticator/9wzdncrfj3rj), and [GAuth](https://5apps.com/gbraad/gauth) which have free apps for iOS, Android, BlackBerry, OS X, Linux, Windows, and Chrome.