> For the complete documentation index, see [llms.txt](https://docs.simptel.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.simptel.com/human-identity/authentication-service/internal-authenticators/phone-based-authentication.md).

# Phone-based authentication

### 📱 Phone-Based Authentication

This section describes the configuration and behavior of **phone authentication**, which enables users to authenticate via **SMS** or **voice calls** using one-time passcodes (OTP).

***

#### ✅ Supported Methods

* **SMS**: A one-time code is sent via text message to the user's phone.
* **Voice**: A one-time code is delivered via an automated voice call that reads the code aloud.

***

#### 🌍 Global Availability

* **All countries are supported.**
* **Per-country restrictions are not currently configurable.**

> 📌 *Make sure your SMS/voice provider has global routing and supports compliance (e.g., local regulations, sender ID requirements, etc.) for the countries you serve.*

***

#### ⚙️ Configuration

| Feature                  | Description                                          |
| ------------------------ | ---------------------------------------------------- |
| **Delivery Channels**    | `sms` or `voice`                                     |
| **From number**          | A e164+ number                                       |
| **From name (optional)** | A human identifier for the number, sometime accepted |
| **Digits**               | **6 or 8**                                           |
| **Template**             | code: %otp%                                          |
| **Integration Provider** | Configured Twilio Account                            |
| **Expiry time**          | 60, 120 and 300 seconds                              |

***

#### ⚠️ Security Notes

* Note: SMS and voice OTPs are **vulnerable to SIM swap attacks** and should not be the sole factor


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter:

```
GET https://docs.simptel.com/human-identity/authentication-service/internal-authenticators/phone-based-authentication.md?ask=<question>&goal=<endgoal>
```

`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal.

The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.