# OTP

For phone-based OTP (one-time password) authentication — where an OTP is a single-use 6-digit code sent to verify the identity of a user — Wise supports multiple delivery methods, including SMS, WhatsApp, and voice. Use Wise's secure endpoint to [create](/api-reference/sca-otp/usersecurityphonenumbercreate) and register the end user's phone number. Then, call the trigger endpoints ([SMS](/api-reference/sca-otp/ottsmstrigger), [WhatsApp](/api-reference/sca-otp/ottwhatsapptrigger), [Voice](/api-reference/sca-otp/ottvoicetrigger)) to send an OTP to the registered number. Finally, submit the OTP via the verify endpoints ([SMS](/api-reference/sca-otp/ottsmsverify), [WhatsApp](/api-reference/sca-otp/ottwhatsappverify), [Voice](/api-reference/sca-otp/ottvoiceverify)) to complete the authentication challenge.

Please read the [SCA over API guide](/guides/developer/auth-and-security/sca-over-api) to understand how SCA integration works.