Auth0 provides a built-in enrollment and authentication flow using Universal Login. However, if you want to create your own user interface, you can use the MFA API to accomplish it. When email is enabled as a factor, all users with verified emails will be able to use them to complete MFA.

Availability varies by Auth0 plan

Both your specific login implementation and your Auth0 plan or custom agreement affect whether this feature is available. To learn more, read Pricing.

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Prerequisites

Before you can use the MFA APIs, you’ll need to enable the MFA grant type for your application. Go to Auth0 Dashboard > Applications > Advanced Settings > Grant Types and select MFA.

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Enroll with email

To enable users to enroll emails in addition to their verified email in their primary identity, you need to complete the following steps.

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Get MFA token

Depending on when you are triggering enrollment, you can obtain an for using the MFA API in different ways:

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Enroll authenticator

Make a POST request to the MFA Associate endpoint to enroll the user’s authenticator. The bearer token required by this endpoint is the MFA token obtained in the previous step. Use the following parameters:
ParameterValue
authentication_types[oob]
oob_channels[email]
emailemail@address.com, the users email address.
curl --request POST \
  --url 'https://{yourDomain}/mfa/associate' \
  --header 'authorization: Bearer MFA_TOKEN' \
  --header 'content-type: application/json' \
  --data '{ "authenticator_types": ["oob"], "oob_channels": ["email"], "email" : "email@address.com" }'
If successful, you receive a response like this: 
{
    "authenticator_type": "oob",
    "binding_method": "prompt",
    "oob_code" : "Fe26..nWE",
    "oob_channel": "email",
    "recovery_codes": [ "N3BGPZZWJ85JLCNPZBDW6QXC" ]
  }
If you get a User is already enrolled error, the user already has an MFA factor enrolled. Before associating another factor with the user, you must challenge the user with the existing factor. If this is the first time the user is associating an authenticator, you’ll notice the response includes recovery_codes. Recovery codes are used to access the user’s account in the event that they lose access to the account or device used for their second-factor authentication. These are one-time usable codes, and new ones are generated as necessary.

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Confirm email enrollment

The user should receive an email containing the 6-digit code that they can provide to the application. To complete the enrollment, make a POST request to the /oath/token endpoint. Include the oob_code returned in the previous response and the binding_code with the value in the email message. 
curl --request POST \
  --url 'https://{yourDomain}/oauth/token' \
  --data grant_type=http://auth0.com/oauth/grant-type/mfa-oob \
  --data 'mfa_token={mfaToken}' \
  --data 'oob_code={oobCode}' \
  --data 'binding_code={userEmailOtpCode}' \
  --data 'client_id={yourClientId}' \
  --data 'client_secret={yourClientSecret}'
If the call was successful, you’ll receive a response in the following format, containing the access token: 
{
  "id_token": "eyJ...i",
  "access_token": "eyJ...i",
  "expires_in": 600,
  "scope": "openid profile",
  "token_type": "Bearer"
}
At this point, the authenticator is fully associated and ready to be used, and you have the authentication tokens for the user. You can check at any point to verify whether an authenticator has been confirmed by calling the MFA Authenticators endpoint. If the authenticator is confirmed, the value returned for active is true. Optionally, you can customize the emails that users receive. See Customize Email Templates for details.

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Challenge with email

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Get MFA token

Get an MFA token following the steps described in Authenticate With Resource Owner Password Grant and MFA.

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Retrieve enrolled authenticators

To challenge the user, you need the authenticator_id for the factor you want to challenge. You can list all enrolled authenticators using the MFA Authenticators endpoint: 
curl --request GET \
  --url 'https://{yourDomain}/mfa/authenticators' \
  --header 'authorization: Bearer MFA_TOKEN' \
  --header 'content-type: application/json'

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Challenge user with OTP

To trigger an email challenge, POST to the MFA Challenge endpoint using the corresponding authenticator_id and the mfa_token. 
curl --request POST \
  --url 'https://{yourDomain}/mfa/challenge' \
  --data '{  "client_id": "{yourClientId}",  "client_secret": "{yourClientSecret}",  "challenge_type": "oob",  "authenticator_id": "email|dev_NU1Ofuw3Cw0XCt5x", "mfa_token": "{mfaToken}" }'

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Complete authentication using received code

If successful, you receive the following response: 
{
  "challenge_type": "oob",
  "oob_code": "abcd1234...",
  "binding_method": "prompt"
}
Your application should prompt the user for the code and send it as part of the request in the binding_code parameter in the following call to the oauth``/token endpoint: 
curl --request POST \
  --url 'https://{yourDomain}/oauth/token' \
  --header 'content-type: application/x-www-form-urlencoded' \
  --data grant_type=http://auth0.com/oauth/grant-type/mfa-oob \
  --data 'client_id={yourClientId}' \
  --data 'client_secret={yourClientSecret}' \
  --data 'mfa_token={mfaToken}' \
  --data 'oob_code={oobCode}' \
  --data 'binding_code={userEmailOtpCode}'
If the call was successful, you’ll receive a response in the format below, containing the access token: 
{
  "id_token": "eyJ...i",
  "access_token": "eyJ...i",
  "expires_in": 600,
  "scope": "openid profile",
  "token_type": "Bearer"
}

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Learn more