Fundamentals BroadNet answer

What is voice OTP?

Last reviewed September 24, 20261 min readReviewed by BroadNet engineering

Quick answer

Voice OTP delivers a one-time passcode as an automated phone call that reads the code aloud, rather than as a text message. It is used as a fallback when SMS is undelivered or unsupported, for landlines and feature phones, and for accessibility — ensuring a user can still verify when a text cannot reach them. It is a core part of a resilient, multi-channel verification flow.

Plain-language definitionVendor-neutralReviewed September 24, 2026

DiagramThe OTP journey, with channel fallback

User requests a codeSign-in, payment or sign-up
Your app calls the verify APIOne request per code
BroadNet delivers the codeOn the best available channelFallback if undeliveredSMSWhatsAppVoice
User enters the codeChecked against the issued code
VerifiedAccess granted

The long answer

Everything worth knowing, nothing that isn't.

§01

How it works

The platform places an automated call to the user's number and a text-to-speech voice reads the code, usually twice, with the option to repeat. Because it rides the voice network rather than SMS routes, it reaches numbers and situations SMS cannot. See /answers/programmable-voice.

§02

When to use it

Voice OTP shines as a fallback: when an SMS code is not delivered within a few seconds, when the number is a landline, or when the user requests it. It also serves accessibility needs for users who cannot read a screen easily. See /answers/best-channel-for-otp.

§03

Part of a verification waterfall

The strongest flows cascade channels — for example silent network authentication or SMS first, then voice — so a single failed channel never blocks a login. See /answers/silent-network-authentication and /answers/sms-fallback-strategy.

§04

Security and rate limiting

Like SMS OTP, voice OTP should be rate-limited per number to resist abuse and pumping, expire quickly, and be single-use. See /answers/sms-otp-best-practices.

BNWritten by the BroadNet engineering team·Operating carrier-grade messaging since 2003, headquartered in Dubai·Editorial standards

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