Getting Started with SMS API — SMS API Docs

Overview

StartMessaging’s SMS API lets you send transactional and OTP messages across India at Rs 0.25 per SMS. We support both DLT-registered and DLT-free (pre-registered) messaging.

Prerequisites

A StartMessaging account with SMS service enabled.
An API Key generated from your dashboard (prefixed with sm_live_).

Step 1: Choose Your Route

| Feature | DLT Free OTP | DLT Route | |---------|---------------|-----------| | Setup time | Instant (< 5 minutes) | 3-7 business days | | DLT registration | Not required | Required by TRAI | | Sender ID | Shared ID | Custom branded ID | | Price | Rs 0.25/SMS | Rs 0.18/SMS | | Endpoint | POST /otp/send | POST /otp/send |

Step 2: Send Your First OTP

All API requests require your API key passed in the X-API-Key header.

Request

curl -X POST https://api.startmessaging.com/otp/send \
  -H "Content-Type: application/json" \
  -H "X-API-Key: sm_live_your_api_key_here" \
  -d '{
    "phoneNumber": "+919876543210",
    "templateId": "YOUR_TEMPLATE_ID",
    "variables": {
      "otp": "123456",
      "appName": "YourApp"
    }
  }'

Response

{
  "success": true,
  "statusCode": 201,
  "requestId": "req_abc123",
  "timestamp": "2026-02-15T10:30:00.000Z",
  "data": {
    "otpRequestId": "uuid-of-otp-request",
    "messageId": "uuid-of-message",
    "status": "queued"
  }
}

Step 3: Check Delivery Status

You can check the real-time delivery status of any message by polling the status endpoint with the messageId returned from the send request.

Request

curl https://api.startmessaging.com/messages/uuid-of-message \
  -H "X-API-Key: sm_live_your_api_key_here"

Response

{
  "success": true,
  "statusCode": 200,
  "data": {
    "messageId": "uuid-of-message",
    "status": "delivered",
    "deliveredAt": "2026-02-15T10:30:05.000Z",
    "error": null
  }
}