Voice OTP Service: Read the Code Aloud in a Phone Call
When an OTP SMS is slow to arrive, or a user cannot read it, a voice OTP calls the number and reads the code aloud. Add it as a Call me instead button beside your SMS OTP. Pricing is per call, on request.
Voice OTP is a one-time password delivered by an automated phone call instead of a text. A text-to-speech voice reads the code, usually twice, digit by digit. Apps offer it as a backup when the SMS has not arrived within a minute, and for users on landlines. We set it up per account, billed per call.
Backup for SMS OTP
Users tap Call me instead when the SMS has not arrived in time.
Works on any phone
Landlines and basic phones can take a call even when they cannot read SMS.
Read digit by digit
The code is spaced out and repeated, so users can type it as they listen.
Status for every call
Each call returns a delivery report, so you can see answered and failed calls.
When voice OTP helps
SMS is the right first channel for OTPs. It is cheap, fast and works on every mobile. But some users still get stuck: the SMS is late on a weak network, their phone's spam filter hides it, or they signed up with a landline number. Each of those users is a lost sign-up or a support call.
A voice OTP gives them a second way in. After 30 to 60 seconds without a code, your screen shows a Call me instead link. The user taps it, the phone rings, and a clear voice reads the code.
- Users on weak networks where SMS arrives late
- Landline numbers on business or government forms
- Older users and people with low vision who find small text hard to read
- Bank and insurance customers who prefer to hear a code
- International users where SMS routes are slow
How it works with your app
Your app creates the OTP and stores it with an expiry time, exactly as it does for SMS. To send it by voice, your server calls our voice API with the mobile number and the text to read, such as Your AcmeIn code is 4 8 2 9 1 3. I repeat, 4 8 2 9 1 3.
The platform places the call, a text-to-speech voice reads your text when the call is answered, and a delivery report comes back with the call status. The fallback decision stays in your app. You choose when to show the button and how many calls a user may request, so voice is only used, and billed, when it is needed.
Writing a script that people can follow
Write the digits with spaces so the voice reads them one at a time, and read the code twice. Say who is calling in the first words, before the code, so the user knows the call is genuine. Keep it under 15 seconds.
Add a warning that your company will never ask for the code. Fraudsters use fake calls to trick people into reading OTPs back, so a line such as Do not share this code with anyone protects your users and your brand. Tell us the languages you need, and we will confirm which voices are available before you go live.
Rules for voice calls in India
TRAI's rules separate promotional calls from service and transactional calls, and ordinary 10-digit mobile numbers may not be used for either. Promotional calls come from 140-series numbers. Service calls from banks, NBFCs, insurers and other regulated financial firms must use 1600-series numbers since early 2026, and other sectors are moving to a new 1601 series from August 2026. Automated calls must also be declared in advance.
An OTP call is a service call, so it must never carry an offer or a sales message. Our team confirms the calling number and the rules that apply to your business during setup. Read our guide to TRAI rules for the full timeline.
Voice OTP pricing
Voice OTP is billed per call from a voice balance on your account, and the rate depends on your volume. Because most users still get the SMS, calls are usually a small share of your OTP traffic. Share your monthly OTP volume and how often users fail to receive the SMS today, and we will quote a rate plus 18% GST.
Sending outside India too?
We also send SMS and WhatsApp messages to customers abroad, with help on each country's sender ID and consent rules.
How it works
Ask for voice OTP
Share your OTP volume and countries. We enable voice on your account and confirm the rate.
Write the script
Brand name first, digits spaced out, code read twice, and a do-not-share warning.
Add the fallback
Show Call me instead after 30 to 60 seconds and call our voice API from your server.
Watch the reports
Track answered and failed calls, and cap calls per number to stop abuse.
Frequently asked questions
What is voice OTP?
Voice OTP is a one-time password delivered by an automated phone call. When the user answers, a computer voice reads the code aloud, usually twice and digit by digit. It is mostly used as a backup when an OTP SMS has not arrived, and for users with landlines or difficulty reading small text.
Does voice OTP replace SMS OTP?
No. SMS should stay the first channel because it is cheaper and most users receive it within seconds. Voice OTP works best as a backup that the user chooses, through a Call me instead link shown after 30 to 60 seconds. That keeps call costs low while rescuing users who would otherwise give up.
Does the call switch over from SMS automatically?
Your app decides. When the user asks for a call, or when your own timer runs out, your server calls our voice API with the number and the script. Keeping that logic in your app lets you limit calls per user and per hour, which also protects you from fraudsters who try to trigger paid calls in bulk.
Can the OTP be read in Hindi or Tamil?
The code is read by a text-to-speech voice, and the languages available depend on the voice route. Tell us which languages your users need during setup and we will confirm what is available. Digits read clearly in English are understood by most users across India.
How much does voice OTP cost?
Voice OTP is billed per call and quoted on request, based on your volume and the countries you call. Since most users still receive the SMS, voice calls are usually a small part of your OTP spend. Share your monthly OTP volume and current SMS failure rate for a quote.
How do I stop abuse of voice OTP?
Limit calls per number, per IP address and per device in your app, add a cooldown before a second call, and put a captcha before the first OTP request. Watch for bursts of calls to unusual number ranges or countries. Our OTP security guide explains these controls in more detail.
Related pages
Rescue users whose OTP SMS never arrives
Add a Call me instead option beside your SMS OTP. Tell us your OTP volume for a per-call quote.