SMSBOX — OTP & verification via SMS

Secure verification with SMS OTP codes

Protect logins, sign-ups and transactions with one-time codes sent by SMS. High delivery speed thanks to direct Belgian routing — 98% of codes are delivered within 3 minutes. SMSBOX generates and validates the code for you — verification is free.

Try the OTP tester API documentation Try it free Pricing

98% Open rate within 3 minutes

200+ Countries reachable worldwide

Free Verification of OTP codes

Applications

OTP via SMS is the standard for two-factor authentication and sensitive actions. No extra app required — it works on every phone.

Two-factor authentication (2FA)

A second security layer at login, on top of the password.

Account creation

Verify phone numbers when new users register.

Transaction verification

Confirm payments, transfers and critical actions.

Password reset

Recover a password securely, without vulnerable e-mail flows.

How does it work?

Request a code

Your application calls POST /v2/otp/send with the user's phone number. SMSBOX generates and sends the code.

The user enters the code

The user receives the SMS and enters the code on your website or in your application.

Verify the code

You call GET /v2/otp/verify with the code entered. Verification is completely free.

Integrate in minutes

Two endpoints: one for sending and one for verifying. SMSBOX generates and stores the code itself — you do not need to set up any code management of your own. Includes the official PHP SDK and code samples for Python, Node.js, C# and PowerShell.

API documentation PHP SDK

1. Send OTP

POST https://core.smsbox.be/api/v2/otp/send X-Api-Key: YOUR_API_KEY Content-Type: application/json { "number": "32496123456" }

2. Verify OTP (free) GET https://core.smsbox.be/api/v2/otp/verify?otp=482913 X-Api-Key: YOUR_API_KEY

SMS OTP versus the alternatives

  SMS OTP  Works on every phone
 No app installation needed
 High open rate (98%)
 Ready to use immediately
 Works offline (no wi-fi)
 

Authenticator app

No cost per code
Requires an app installation
Setup hurdle for users
Lost when switching phones
Not suited to one-off flows

E-mail OTP

No cost per code
Slow delivery (spam filters)
Low open rate (~20%)
Vulnerable to phishing
No channel separate from the password

Price per verification code

What does it cost?

One verification code is one SMS. You only pay for the messages you send, with prepaid credits: no subscription, no setup costs. Checking the code is free.

One SMS to Belgium or the Netherlands costs 1,6 credits; the bigger the package, the lower the price per message
Prepaid credits, no subscription or setup fee
Credits stay valid for one year

from

€ 0,06

per message to Belgium, excl. VAT View credit packages Try it for free

Starting price at high volumes. All prices excl. 21% VAT.

Frequently asked questions

What is an OTP code?

OTP stands for One Time Password — a one-off password that is valid only once and typically expires within a few minutes. It is used to verify a user's identity at login, registration or sensitive actions.

How fast does an OTP SMS arrive?

In Belgium, on average under 5 seconds thanks to direct operator connections. Worldwide, 98% of messages arrive within 3 minutes. For OTP this is crucial — a code that arrives too late is almost always useless to the user.

Who generates the OTP code?

SMSBOX generates the code for you — you do not need to build any logic for generating, storing or expiring codes. You call /v2/otp/send with the number, and later /v2/otp/verify with the code the user entered. Verification is free.

What does an OTP SMS cost?

Sending an OTP is billed like a regular SMS message — from €0.06 per message to Belgium at high volumes. Verifying an OTP code is completely free. See the price list for other countries.

Do I get a report per code sent?

Yes, a delivery report is available via webhook for every message sent. That way you know whether the code was actually delivered to the user's device.