SMS OTP and Mobile Verification

Textbelt is a no-nonsense API built for developers who want to send account verification SMS.

Thousands of clients prefer Textbelt over other SMS providers for our ease of setup, simple, predictable pricing packages, and personal support. Since its creation, Textbelt has sent millions of OTPs on behalf of thousands of companies.

We handle both steps of mobile identity and two-factor verification:

1. Send an SMS verification code - generate a one-time code and send it to the user's phone.
2. Verify the code - check the user's input against the code you just sent.

Create an API key   View pricing

$ curl -X POST https://textbelt.com/otp/generate \
       --data-urlencode phone='5555555555' \
       --data-urlencode userid='myuser@site.com' \
       -d key=example_otp_key

import requests
resp = requests.post('https://textbelt.com/otp/generate', {
  'phone': '5555555555',
  'userid': 'myuser@site.com',
  'key': 'example_otp_key',
})
print(resp.json())

require 'net/http'
require 'uri'

uri = URI.parse("https://textbelt.com/otp/generate")
Net::HTTP.post_form(uri, {
  :phone => '5555555555',
  :userid => 'myuser@site.com',
  :key => 'example_otp_key',
})

var request = require('request');
request('https://textbelt.com/otp/generate', {
  body: {
    phone: '5555555555',
    userid: 'myuser@site.com',
    key: 'example_otp_key',
  },
})

using System;
using System.Collections.Specialized;
using System.Net;

using (WebClient client = new WebClient())
{
  byte[] response = client.UploadValues("http://textbelt.com/text", new NameValueCollection() {
    { "phone", "5555555555" },
    { "userid", "myuser@site.com" },
    { "key", "example_otp_key" },
  });

  string result = System.Text.Encoding.UTF8.GetString(response);
}

$ch = curl_init('https://textbelt.com/otp/generate');
$data = array(
  'phone' => '5555555555',
  'userid' => 'myuser@site.com',
  'key' => 'example_otp_key',
);

curl_setopt($ch, CURLOPT_POST, 1);
curl_setopt($ch, CURLOPT_POSTFIELDS, http_build_query($data));
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);

$response = curl_exec($ch);
curl_close($ch);

final NameValuePair[] data = {
    new BasicNameValuePair("phone", "5555555555"),
    new BasicNameValuePair("userid", "myuser@site.com"),
    new BasicNameValuePair("key", "example_otp_key")
};
HttpClient httpClient = HttpClients.createMinimal();
HttpPost httpPost = new HttpPost("https://textbelt.com/otp/generate");
httpPost.setEntity(new UrlEncodedFormEntity(Arrays.asList(data)));
HttpResponse httpResponse = httpClient.execute(httpPost);

String responseString = EntityUtils.toString(httpResponse.getEntity());
JSONObject response = new JSONObject(responseString);

Customizing your OTP

There are a few parameters you can add to your /otp/generate request:

• message will replace the default OTP message. Use the $OTP variable to include the OTP.
• lifetime will determine how many seconds the OTP is valid for. If you set lifetime to 240, the OTP will be valid for 240 seconds or 4 minutes.
• length specifies the number of digits in your OTP.

$ curl -X POST https://textbelt.com/otp/generate \
         --data-urlencode phone='5557727420' \
         --data-urlencode userid='myuser@site.com' \
         --data-urlencode message='Nuclear launch code: $OTP! Use it to login.' \
         -d lifetime=120 \
         -d length=4 \
         -d key=example_otp_key

Response Details

Example API response from the OTP generation endpoint /otp/generate:

{"success": true, "textId": "1234", "quotaRemaining": 70, "otp": "672383"}

Check success to determine whether the OTP was sent to the user. This means the user was sent a text containing an OTP. By default the message format is: "Your verification code is 672 383".

Example out-of-quota or invalid key response from /otp/generate:

{"success": false, "quotaRemaining": 0, "otp": ""}

Here's an example valid OTP response from OTP verification endpoint /otp/verify. Check isValidOtp to decide whether the OTP has been approved:

{"success": true, "isValidOtp": true}

Here's an example response for an invalid OTP. Note that "success" indicates a successful API response, not a successful OTP:

{"success": true, "isValidOtp": false}

Get started

OTP keys are the same as normal Textbelt keys. This means you can mix and match your quota to send OTPs and normal text messages. Create an API key to start sending and receiving SMS:

Generate an API key

Get in touch

Any questions? Email support@textbelt.com or read the FAQ.