Passwordless Authentication with Magic Links

Passwordless Authentication with Magic Links

When implementing passwordless authentication with "magic links", the user is sent an email with a link in it. This link will allow them to login directly when clicking on it. It is similar in function to them getting an email with a one-time-use code in it, returning to your app, and entering the code, but without having to actually perform those steps.

With magic link transactions, both the initial request and its response must take place in the same browser or the transaction will fail. This is particularly relevant for iOS users, who cannot change their default web browser. For example, the user might make the initial request using the Chrome browser, but when the user opens the magic link in their email, iOS automatically opens it in Safari (the default browser). If this happens, the transaction will fail.

With an email connection, the user is asked to enter their email address, to which Auth0 usually sends a one-time-use code. Instead, you can configure Auth0 to send a magic link. If you are using Universal Login, make sure you configure Universal Login with Passwordless.

Send Magic Link Flow

Sample Magic Link Email

The user then clicks the button or link in the email and is automatically signed in to your application.

Magic Link User Flow

Configure the connection

  1. Navigate to Auth0 Dashboard > Authentication > Passwordless, and enable the Email switch.

Enable Email Passwordless

  1. Select your Email Syntax, and enter your email's From, Subject, and Message text.

Configure Email Passwordless

  1. Enter any Authentication Parameters you would like to include in the generated sign-in link.

  2. Adjust settings for your OTP Expiry and OTP Length

  • Only the last one-time password (or link) issued will be accepted. Once the latest one is issued, any others are invalidated. Once used, the latest one is also invalidated.
  • Only three failed attempts to input the one-time password are allowed. After this, a new code will need to be requested.
  • The one-time password issued will be valid (by default) for three minutes before it expires.
  • If you choose to extend the amount of time it takes for your one-time password to expire, you should also extend the length of the one-time password code. Otherwise, an attacker has a larger window of time to attempt to guess a short code.
  1. Decide if you want to Disable Signups. You can enable passwordless access just for existing users by enabling this setting.

Multi-language support

The Message area supports multiple languages.

To choose the language, call the /passwordless/start authentication endpoint and set the value of the 'x-request-language' header. When this header is not set, the language is extracted from the 'accept-language' header, which is automatically set by the browser.

Message syntax

The Message area accepts Liquid syntax. You can use this syntax, combined with exposed parameter values, to programmatically construct elements of the message. For example, you can reference the request_language parameter to change the language of the message:

{% if request_language contains 'dutch' %}
   Hier is uw verificatie code: {{ code }}
{% endif %}

{% if request_language contains 'fr-FR' %}
   Ceci est votre code: {{ code }}
{% endif %}

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The following parameters are available when defining the message template:

Exposed Parameter Description
code The password to use
link The generated sign-in link The name of the application with which the user is signing up
request_language The requested language for message content
operation Indicates when the template has been triggered by an update to a user's email via the API. Equals change_email when triggered; otherwise, null.

Enable your apps

Select the Applications view, and enable the applications for which you would like to use Passwordless Email.

Email Providers

By default, Auth0 sends the email from its own SMTP provider. Auth0's built-in email infrastructure should be used for testing-level emails only. You can configure your own email provider to better monitor and troubleshoot the email service as well as be able to fully customize the emails.

You may configure Auth0 to send users one-time codes using: