---
updatedAt: 2026-06-24T07:14:54.000Z
agentTools:
  projectIndex: https://developers.youtrust.com/llms.txt
---

# Authentication mode

# Authentication modes available

We offer several methods to authenticate your signers, depending on the Signature Level you choose, your documents' security requirements and the availability of the Signers phone number.

**Three methods are available** when it comes to authentication:

* One-time-Password (OTP) sent by SMS
* One-time-Password sent by Email
* No One-time-Password

The availability of these different methods **depends on the Signature Level**, as shown in the table below.

<Table align={["left","left","left"]}>
  <thead>
    <tr>
      <th>
        Signature Level
      </th>

      <th>
        Available authentication modes
      </th>

      <th>
        Comment
      </th>
    </tr>
  </thead>

  <tbody>
    <tr>
      <td>
        **Simple eSignature**
      </td>

      <td>
        * `no_otp`
        * `otp_email`
        * `otp_sms`
      </td>

      <td>
        Signers authentication only (no identification). Ideal for most signature requests.

        Those options are available:

        * One-time-Password sent by SMS
        * One-time-Password sent by Email
        * One-time-password by email or SMS should only be used for documents requiring a higher level of security.
      </td>
    </tr>

    <tr>
      <td>
        **Advanced eSignature**
      </td>

      <td>
        * `otp_sms`
      </td>

      <td>
        Signers will be identified by an identity check (ID document).

        The One-time-Password sent by SMS is mandatory.
      </td>
    </tr>

    <tr>
      <td>
        **Qualified eSignature**
      </td>

      <td>
        * `null`
      </td>

      <td>
        Signers are identified by a double identity check (ID document and video face verification) or with their saved identity registered after their first identification.

        Authentication with an OTP code is not relevant for this level of signature, as we perform a video verification of the face. However, this verification will require a mobile phone with a camera. Please ensure that the signer has one with them.
      </td>
    </tr>
  </tbody>
</Table>

The authentication mode is set at the signers level, in the **signature\_authentication\_mode** property in the signer payload.\
It can be different for each signer.

<Table align={["left","left","left"]}>
  <thead>
    <tr>
      <th>
        Mode
      </th>

      <th>
        signature_authentication_mode
      </th>

      <th>
        Comment
      </th>
    </tr>
  </thead>

  <tbody>
    <tr>
      <td>
        One-time-Password sent by SMS
      </td>

      <td>
        `otp_sms`
      </td>

      <td>
        Signer `phone_number` is required.  
        Not available for Signers in China 🇨🇳
      </td>
    </tr>

    <tr>
      <td>
        One-time-Password sent by Email
      </td>

      <td>
        `otp_email`
      </td>

      <td>
        Signer `phone_number` is optional
      </td>
    </tr>

    <tr>
      <td>
        No One-time-Password
      </td>

      <td>
        `no_otp`
      </td>

      <td>
        Signer `phone_number` is optional
      </td>
    </tr>
  </tbody>
</Table>

<br />

### ⚠️ Limited list of authorised countries during free trial period

During the free trial period, one-time-Password sent by SMS (`otp_sms`) are restricted to phone numbers from the following countries:

*Austria, Belgium, France, French Polynesia, Germany, Guadeloupe, Italy, Luxembourg, Martinique, New Caledonia, Portugal, Reunion, Spain, Switzerland, United-Kingdom.*

SMS OTP delivery to **all other countries is not supported** during the free trial period.

<br />

### Example of Signer creation with the 3 authentication methods

In the following example, we have added 3 Signers, each with a different `signature_authentication_mode`.

[**POST /signature\_requests/\{signatureRequestId}/signers**](https://developers.yousign.com/reference/post-signature_requests-signaturerequestid-signers-1)

```json JSON (otp_sms)
{
    "info": {
        "first_name": "John",
        "last_name": "Doe",
        "email": "john.doe@example.com",
        "phone_number": "+33700000000",
        "locale": "en"
    },
  	"signature_level": "electronic_signature",
    "signature_authentication_mode": "otp_sms"
}
```
```json JSON (otp_email)
{
    "info": {
        "first_name": "Jane",
        "last_name": "Doe",
        "email": "jane.doe@example.com",
        "locale": "en"
    },
  	"signature_level": "electronic_signature",
    "signature_authentication_mode": "otp_email"
}
```
```json JSON (no_otp)
{
    "info": {
        "first_name": "Jane",
        "last_name": "Doe",
        "email": "jane.doe@example.com",
        "phone_number": "+33700000000",
        "locale": "en"
    },
  	"signature_level": "electronic_signature",
    "signature_authentication_mode": "no_otp"
}
```

***

# Updating the authentication mode

Updating the authentication with [**PATCH /signature\_requests/\{signatureRequestId}/signers**](ref:patch-signature_requests-signaturerequestid-signers-signerid-1#/) is only available for the Simple eSignature (SES) as long as the Signer has not signed the Signature Request.

Updating the authentication for AES and QES is not permitted as the AES requires an OTP by SMS, and the QES requires no OTP.

<Callout icon="💡" theme="default">
  If you change the authentication mode while the Signer is on the signature step in the signing flow, the old mode is immediately invalidated and the new mode applies.
</Callout>

<AskAIBanner label="Ask AI about it" question="" title="Not sure which authentication mode to use?" />

# Sub pages

* [Custom One-Time Password (OTP) SMS](https://developers.youtrust.com/docs/custom-otp-sms.md)