Reverse OTP providers: seven compared.
Only a handful of providers let users send the code instead of receiving it, and they differ in channels, prices and regions. This guide compares seven reverse OTP providers based on their own websites: which channels they support, what they charge and who they are built for.
- What counts as reverse OTP
- Seven providers at a glance
- How to choose
Christian Schätzlein, Founder and developer of Sendity
3 min read
Seven providers, user sends
Channel and price per verification, as of 3 Nov 2026
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Sendity WhatsApp, email; SMS optional €0.02
Per verified number, €0.005 per email address. Open source, self-hostable.
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phone-verif WhatsApp €0.015
Per success, down to €0.010 in large packages. WhatsApp only.
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Contiguity SMS, iMessage free*
*According to the provider; depending on the plan, a number of your own costs extra. US focus.
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smsmode SMS to a rented number rental
French provider; you pay for the virtual number.
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VerifyKit Inbound SMS no price
No public price for the inbound flow.
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OTPless WhatsApp no price
Focus on India.
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Exotel Missed call to a number no price
Focus on India, Middle East, Africa.
Sign-ups by message. No form, no code.
Sendity is a sign-up widget for your website. Instead of filling in a form, your visitors send one short message via WhatsApp or email. Sendity checks who it came from and hands your site the name and the confirmed phone number or email address.
See how Sendity works →-
One message instead of a form Visitors tap send in WhatsApp or their email app. Nothing to type, no confirmation email to click.
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Confirmed by the message itself The contact comes from the sender of the message, so typos and made-up addresses never reach your list.
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Pay per confirmed contact Start with 1,000 free credits, no credit card. After that, prepaid packages with no subscription.
The user sends something to the provider: a message, an email or a call. If the provider calls or texts the user, it is an outgoing method, whatever it is called.
No standard
There is no specification for reverse OTP from standards bodies or messenger operators. Every provider builds its own flow, so compare what actually happens, not the name.
Not reverse: flash calls
Many large messaging platforms offer flash or missed calls, but there the provider calls the user. We left these out, as well as providers that only send codes.
Channels
Most providers support one channel: WhatsApp, SMS or a missed call. Contiguity adds iMessage. Sendity is the only one in this comparison that also verifies email addresses.
Prices
Three models: per successful verification (phone-verif, Sendity), free with a number you rent (Contiguity, smsmode), or no public price. phone-verif is cheaper than Sendity; Contiguity says its reverse OTP is free.
Region and data
Several providers focus on India or the US. Hardly any states where data is stored. Sendity is open source and can be run on your own servers.
Choosing a provider.
Three questions before the price.
Which channel do your users have?
In Germany, Austria and Switzerland mostly WhatsApp and email, in the US SMS and iMessage.
Phone only, or email too?
If some sign-ups only need an email address, one provider for both saves a second integration.
Where does the data go?
Ask for the data location and a data processing agreement, or host it yourself.
Other providers or Sendity?
Where Sendity differs, and where others are ahead.
| Aspect | Other reverse OTP providers | With Sendity |
|---|---|---|
| Channels | Usually one | WhatsApp and email, SMS optional |
| Email verification | Not offered | Yes, DKIM-checked |
| Price | From free to no public price | €0.02 per number, €0.005 per address |
| Self-hosting | Not stated | Open source |
Based on the providers’ own websites, retrieved on 3 November 2026: sendity.io, phone-verif.com, contiguity.com, smsmode.com, verifykit.com, otpless.com, exotel.com. Prices excluding VAT. We review this comparison every quarter; providers can report corrections to support@sendity.io.
Where Sendity fits.
Not the cheapest, but built for European sign-ups.
Two channels, one widget
Visitors choose WhatsApp or email.
Self-hosting possible
Open source, on your own servers if you need it.
Only success costs
Prepaid without a subscription, failed attempts are free.
Live on your page in minutes.
Sendity runs as a compact widget on your page. Pick the path that fits your website.
Reverse OTP providers: common questions.
Why is Sendity not the cheapest?
phone-verif is cheaper for WhatsApp alone, and Contiguity calls its reverse OTP free. Sendity costs more and adds email verification, campaigns and self-hosting.
Do Twilio or Vonage offer reverse OTP?
Not as a product. You can build it yourself with an inbound number and a webhook, including fraud checks and expiry.
Is a missed call to a number reverse OTP?
Yes, if the user calls you, as with Exotel. A flash call where you call the user is an outgoing method.
Why are some providers missing?
We only list providers whose own website describes a flow in which the user sends. Products that were unreachable or discontinued on the retrieval date are left out.
Keep reading.
Reviewed for accuracy in by Christian Schätzlein.
Reverse OTP with WhatsApp and email.
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