> ## Documentation Index
> Fetch the complete documentation index at: https://docs.rownd.io/llms.txt
> Use this file to discover all available pages before exploring further.

# Sign in with SMS / Phone Number

> Passwordless SMS authentication

SMS-based authentication using Rownd Sign-in Links is a secure and convenient method for users to sign in to their accounts on your website and mobile apps. This approach eliminates the need for passwords, instead sending a unique, one-time-use sign-in link directly to users' mobile devices via SMS. By simply clicking on the link, users can securely access their accounts without having to remember any passwords.

<Note>
  **Enhance SMS Link Trust with Custom Domains**

  Using a custom domain for your SMS authentication links can significantly improve user trust and click-through rates. When users receive links that contain your own domain rather than a generic one, they're more likely to perceive them as legitimate and click through.

  Learn more about setting up [Custom Domains](/configuration/custom-domains/overview) to create a more cohesive branded experience.
</Note>

This authentication method offers several advantages, including ease of use for users and enhanced security. By leveraging users' mobile devices for authentication, you can reduce the risk of password-related security breaches and ensure that only the authorized account holder has access to the account.

Integrating SMS-based authentication with Rownd Sign-in Links is straightforward for developers, and the process is intuitive for users. This results in a streamlined authentication experience on your platform and a reduced barrier to entry for your users.

By incorporating SMS-based authentication with Rownd Sign-in Links, you can offer a user-friendly and secure authentication option that promotes trust in your platform and safeguards user data.

#### When to use phone sign-in

There are few more powerful ways to bridge the computer-to-mobile gap than with SMS sign-in. Rownd utilizes powerful sign-up links that make it easy to verify a phone number without having to copy down annoying 4-8 digit passcodes.

When paired with Rownd's mobile download links, users can leverage SMS to download and sign-in to your mobile app in just a few taps.

#### Enabling SMS authentication

1. Navigate to **Sign-in methods** in the [Rownd dashboard](https://app.rownd.io).
2. Toggle the switch for **Phone number** to the "on" position.
3. Click **Save**.

<Info>
  There is an incremental cost to send SMS text messages. Most Rownd plans include a set number of messages per-month and a small surcharge for each message thereafter. Surcharges may vary based on the destination country / carrier.
</Info>

<Info>
  SMS is disabled for free accounts by default. [Get in touch](https://rownd.io/contact) with us if you'd like to enable it.
</Info>