Authentication Method

The optional authentication_method object can be used for any of the following events:

  • $registration – what method was used to create the user account
  • $login – what method was used to create a new authentication session
  • $challenge – what method was requested from or resolved by the users as additional verification

By sending this information, not only does it provide valuable insight during fraud investigations when used to filter down the dataset as well as configuring policies, but it also helps improve Castle's risk models.





$authenticator, $biometrics, $email, $password, $phone, $push, $security_key, $social, $sso

See below for detailed explanation



Optional description of the method variant, e.g. facebook when type is $social, or sms for $phone

Authentication types

Detailed description of the available options for the type parameter




Google Authenticator, or any other OTP app


Apple FaceID/TouchID, Microsoft Hello, etc


Email confirmation/magic link or PIN code


Knowledge-based authentication, such as security questions


Standard password entry, combined with email, phone, or username


Phone confirmation/magic link or PIN code


Mobile push notification


Yubikey, Google Titan, etc


Social sign-in with Google, Facebook, Apple, etc


SAML, e.g. Okta or Rippling


 // ...
  "authentication_method": {
    "type": "$phone",
    "variant": "sms"

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