Definition
A voice OTP is a one-time password delivered by an automated phone call: a text-to-speech engine reads the code aloud, usually twice, so the user can type it into an app or website to verify their phone number or log in.
The application requests a code, the platform places an outbound call to the user's number and a text-to-speech (TTS) engine reads the digits one by one, often with a short pause between them and an option to repeat. The code itself is generated and checked by the application (or a verification service), exactly as with SMS OTP; only the delivery channel differs.
Voice OTP is mainly used as a fallback. It reaches landlines and feature phones, works when an SMS is filtered or delayed, and helps users with visual impairments. Many businesses offer it as a "Call me instead" option after an SMS or WhatsApp code has not arrived within a set time.
In the GCC and wider MENA, the call should be read in the user's language. Arabic TTS has to pronounce digits clearly and consistently; reading the code digit by digit ("four, seven, one…") avoids the ambiguity of reading it as a number.
Voice OTP carries its own fraud risk. Attackers can trigger calls to premium or high-cost international ranges (international revenue share fraud), so apply the same controls as for SMS: rate limits per number, device and IP, country allowlists, and monitoring of verification completion rates. Under NIST SP 800-63B, OTPs sent over the public telephone network (SMS or voice) are a "restricted" authenticator, so high-risk services should also offer stronger factors.
OmniChannels.ai, through BroadNet's voice capability, offers voice OTP with text-to-speech including Arabic; voice is provisioned with the account team.
Example
"Your verification code is: 4… 7… 1… 9… 0… 2. I repeat: 4… 7… 1… 9… 0… 2."