OTP Verification

Send and verify one-time codes over SMS or WhatsApp. No third-party service needed.

How it works

1. Send a code — Call POST /api/v2/verify with a phone number. SendLime generates a cryptographically random code and delivers it via SMS or WhatsApp.
2. User enters the code — Your app collects the code from the user.
3. Verify the code — Call POST /api/v2/verify/check with the request ID and code. SendLime returns whether the code is valid.

Features

• SMS and WhatsApp — Send OTP codes through either channel.
• Configurable code length — 4 to 10 digits (default: 6).
• Configurable expiry — 60 seconds to 1 hour (default: 5 minutes).
• Attempt limiting — Codes are invalidated after 3 failed attempts.
• Rate limiting — 10 send requests per minute per phone number.
• Localization — English and Bengali message templates.
• Secure — Codes are compared using constant-time comparison to prevent timing attacks.

Pricing

• SMS verification — Standard SMS rate (currently 0.5 BDT per message).
• WhatsApp verification — Free (0 credits).

Balance is charged when the code is sent and refunded automatically if delivery fails.

Quick example

# 1. Send a verification code
curl -X POST "https://api.sendlime.com/api/v2/verify" \
  -H "Authorization: Bearer sl_live_your_key_here" \
  -H "Content-Type: application/json" \
  -d '{"phone_number": "+8801XXXXXXXXX"}'

# Response:
# { "success": true, "data": { "request_id": "vrf_abc123", "to": "+8801XXXXXXXXX", "channel": "sms", "status": "pending", "expires_in": 300 } }

# 2. Verify the code
curl -X POST "https://api.sendlime.com/api/v2/verify/check" \
  -H "Authorization: Bearer sl_live_your_key_here" \
  -H "Content-Type: application/json" \
  -d '{"request_id": "vrf_abc123", "code": "483921"}'

# Response:
# { "success": true, "data": { "request_id": "vrf_abc123", "to": "+8801XXXXXXXXX", "status": "verified", "verified_at": "2025-01-15T10:30:00.000Z" } }

Using the SDK

import { SendLime } from "@sendlime/node";

const sendlime = new SendLime("sl_live_your_api_key");

// Send a code
const { request_id } = await sendlime.verify.sendCode({
  phone_number: "+8801XXXXXXXXX",
});

// Verify the code
const result = await sendlime.verify.checkCode({
  request_id,
  code: "483921",
});