SMS code is passwordless sign-in: a one-time code sent to the user's phone. The method does nothing until the same environment has an SMS provider connected. Authenticator-app MFA is a separate setting and does not use this method.

## Connect a provider first

In the [Authdog console](https://console.authdog.com), select the project and environment, open **Notifications > Providers**, and select the **SMS** channel. Connect one provider and send its test:

- [Twilio](/marketplace/twilio/setup)
- [Vonage](/marketplace/vonage/setup)
- [MessageBird](/marketplace/messagebird/setup)
- [Amazon SNS](/marketplace/amazon-sns/setup)

The provider you just connected becomes the one that sends. Others you connect later are fallbacks after a hard failure.

## Enable the method

1. Open **Authentication > Methods**.
2. Enable **SMS**.
3. Open the hosted sign-in page for that environment.
4. Request a code for a handset you control and enter it.
5. Confirm the user session is created.

If the test from the provider succeeds and the sign-in code never arrives, the method is on but the active provider is a different environment's. Providers do not copy between environments.

SMS as a second factor, after a password or social sign-in, is configured under **Multi-factor authentication**, not by this method. See [Multi-factor authentication](/docs/mfa).

## Related

| Read | To learn how to |
| --- | --- |
| [Multi-factor authentication](/docs/mfa) | SMS as a second factor |
| [WhatsApp](/marketplace/whatsapp/setup) | The same idea on WhatsApp, through Twilio |
| [Marketplace](/marketplace/sms-otp) | The listing for this integration |