Technical Details

The Number Verification API is Vonage’s standalone Silent Authentication product. It verifies the phone number linked to the SIM card in the device connected to the mobile data network, without any user input.

The Number Verification API authentication process is similar to the one using the silent_auth channel in the Verify API. The mobile application will request an authentication of an end-user’s phone number, at which point a check_url is returned provided to the application back-end that needs to be opened by the mobile application using a mobile data connection. A series of URL redirects must be followed in order to get a successful response from the CSP and Vonage.

If the end-user does not successfully complete the authentication process or is not on a supported network, you can try authenticating the same end-user using a more traditional channel like SMS. Vonage also offers the Verify API, which will automatically retry a different channel if the Silent Authentication attempt is unsuccessful. Please see the Verify API documentation for more details.

Use Cases

The Number Verification API improves service security by simplifying user authentication, removing the need for extra mechanisms such as one-time passwords (OTP) sent over SMS, Voice and email. There are several key benefits of using silent authentication:

• Once an end-user enters their credentials, the rest of the authentication process happens in the background; they do not need to retrieve OTPs from a separate application, providing a seamless user experience.
• It removes the exposure to toll fraud for developers, typically present with SMS and Voice OTP scenarios.

Some use cases where the Number Verification API is useful:

• Protecting against spam, by preventing spammers from creating multiple accounts

• Monitoring suspicious activity, by forcing an account user to verify ownership of a number

• Ensuring that you can reach your users at any time because you have their correct phone number

API Reference

The OpenAPI specification for the Number Verification API is available here.

Getting Started

Check out Getting Started for a step-by-step guide on how to get up and running with the Number Verification API.

Registration

A prerequisite to using Number Verification is the registration of your application with Vonage and the Communication Service Providers (CSP). Vonage’s Network API Registration service automates the registration process through a common dashboard interface and sends the information to the CSPs for approval. Vonage’s Customer Dashboard portal is the single source for registration across all participating CSPs.

More detailed information on how the Registration product works can be found here.

Sandbox

Use the Sandbox to start using the Number Verification API right away. It allows you to work with live data for up to five phone numbers added to an allowlist.

Authentication

See our guide on Client Authentication for code samples and more information on how Client Authentication works.

Using Number Verification in Germany

When using the Number Verification API in Germany, you must include specific wording in your application to gain the user's consent before any IP matching / processing:

English

German

Troubleshooting

No CSRF value available in the session cookie

The authentication flow returns this error:

error: request_forbidden & error_description: The request is not allowed. No CSRF value available in the session cookie

Make sure the redirect_uri set in the dashboard uses https and not http.