With an SMS connection, the user is asked to enter a phone number, to which Auth0 sends a one-time code using Twilio. The user then enters the code into your application.

If the phone number attached to the code matches an existing user, Auth0 authenticates the user:

If the user is new, their user profile is created for the sms connection before they are authenticated by Auth0.

On mobile platforms, your app will receive an ID Token, the user profile, and optionally, a Refresh Token.

You will need a Twilio Account SID and a Twilio Auth Token. These are the Twilio API credentials that Auth0 will use to send an SMS to the user.

1. Navigate to the Connections > Passwordless page in the Auth0 Dashboard, and enable the SMS toggle.

2. Enter your Twilio Account SID and Twilio Auth Token.

3. Select your SMS Source and depending on your selection, enter either your Twilio Messaging Service SID or a From phone number. Users will see what you enter as the sender of the SMS.

4. In Message, enter the body text of the SMS.

5. Adjust settings for your OTP Expiry and OTP Length, and click SAVE.

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.

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:

The following parameters are available when defining the message template:

Exposed Parameter	Description
password or code	The password to use
phone_number	The user's phone number
application.name	The name of the application with which the user is signing up
request_language	The requested language for message content

Click the Apps tab, and enable the apps for which you would like to use Passwordless SMS.

Lock is a widget that allows you to easily integrate Auth0's Passwordless Authentication into your iOS applications.

After installing and configuring Lock.iOS-OSX, you will be able to use Lock as follows.

When this code runs, it will ask the user for their phone number:

Then Auth0 will use Twilio to send to the user an SMS containing the one-time code:

Lastly, the user enters the one-time password into Lock. Then, if the password is correct, the user is authenticated.