> ## Documentation Index
> Fetch the complete documentation index at: https://docs.contiguity.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Use Reverse OTP with iMessage

> Have a user send you a text to verify their phone number

Reverse OTP with iMessage verifies a user's phone number by having the user initiate a message to you over iMessage, rather than you reaching out first. Compared to traditional SMS OTPs, this workflow offers several advantages:

* Sending an iMessage requires the user to use their own Apple device, making it much more difficult for attackers to fake and giving you greater confidence in the user's authenticity.
* You save on operational costs because you’re not paying to have potentially dozens of lines to send outbound OTPs to users.
* iMessage generally has high delivery and reliability rates, especially compared to international SMS, where texts may be blocked or filtered.
* Ratelimits don't apply to inbound iMessage, so you can verify millions of users using just one iMessage-capable line.

<Info>
  Reverse OTP with iMessage requires a leased iMessage-capable line, and an iMessage entitlement.
</Info>

<Card title="Implement Reverse OTP with iMessage" icon="arrow-up-right" href="/api-reference/product/otp/reverse/initiate">
  Read the API documentation for initiating, verifying, and cancelling a Reverse OTP with iMessage session.
</Card>

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