SMS verification online

With SMS verification, a user confirms their identity with a one-time code (OTP) sent by SMS to their mobile number. Only the person holding the device can enter the code — a simple and widely adopted form of two-step verification.

SMS verification works on every phone, without an extra app. Thanks to direct operator connections, 98% of messages arrive within 3 minutes, worldwide in more than 200 countries. Via SMSBOX you send codes from €0.06 per SMS — checking the code is free.

How SMS verification works

Send the code — You send a one-time code to the user's mobile number — via the API (/v2/otp/send) or simply via the web interface. SMSBOX generates the code for you.
User enters the code — The user receives the SMS and enters the code on your website or in your application. The code remains valid for 10 minutes.
Check the code — You check the entered code via the API (/v2/otp/verify). Verifying is completely free.

Discover the OTP API More about the SMS API

What do you use SMS verification for?

Login & 2FA

A second security layer next to the password when logging in.

Registrations

Verify mobile numbers of new users and keep out fake accounts.

Transactions

Confirm payments and sensitive actions with a one-time code.

Password reset

Restore passwords securely via a separate channel, independent of email.

Sending codes or receiving codes?

SENDING codes

Want to verify your own users? With the SMSBOX OTP API you send codes via /v2/otp/send and check them for free via /v2/otp/verify — without having to generate, store or expire codes yourself.

To the OTP API

RECEIVING codes

Want to receive verification codes yourself without giving away your private number? Be careful with disposable-number sites: those numbers are public, so everyone can read your codes — unsafe for your accounts. Your own virtual number at SMSBOX is truly private.

To virtual number

Want to know more about incoming SMS in general? See Receive SMS.

Best practices for SMS verification

Limited validity — Let codes expire quickly so an intercepted code becomes worthless. At SMSBOX an OTP code remains valid for 10 minutes.
Rate limiting — Limit the number of send and verification attempts per user to counter abuse and SMS pumping.
Clear message text — Mention your brand name and the purpose of the code. In your message text you use the {OTP} placeholder where the code should appear.

Frequently asked questions about SMS verification

What is SMS verification?

With SMS verification, a user confirms their identity with a one-time code (OTP) sent by SMS to their mobile number. Only the person holding the device can enter the code — a simple and widely adopted form of two-step verification.

What is the difference between OTP, 2FA and MFA?

An OTP (One Time Password) is the one-time code itself. 2FA (two-factor authentication) is the principle of requiring a second factor in addition to a password — for example that OTP via SMS. MFA is the broader term for two or more factors.

What does SMS verification cost via SMSBOX?

Sending a verification code is billed as a regular SMS message, from €0.06. Checking (verifying) the code is completely free, and SMSBOX generates and manages the codes for you.

Can I receive verification SMS on a virtual number?

Yes, with your own virtual number you receive verification codes online without giving away your private number. That is safer than public disposable-number sites, where anyone can read the codes. Some services do block certain number ranges.

How fast does a verification code arrive?

In Belgium, on average under 5 seconds thanks to direct operator connections; worldwide, 98% of messages arrive within 3 minutes. The code remains valid for 10 minutes.