What is a transactional SMS API? A transactional SMS API lets your application automatically send service messages such as OTPs, order updates and payment alerts to a customer's phone. These messages are triggered by a customer's action, can reach numbers on the DND list, and must use DLT-approved templates in India.
Transactional SMS API for OTP, Alerts & Critical Business Notifications
Send instant OTP SMS, transactional alerts, and system notifications with 99.9% uptime using our secure, high-speed SMS API platform built for enterprise reliability.
What is Transactional SMS API?
Transactional SMS API is a programmable messaging service that enables businesses to send automated, time-critical messages such as OTPs (one-time passwords), transaction alerts, order confirmations, and system notifications directly to users' mobile phones via HTTP REST API. Unlike promotional SMS which is used for marketing, transactional SMS is designed for essential business communications and offers several critical advantages:
Instant Priority Delivery
Messages are sent within 2-5 seconds via dedicated priority routes (vs 5-30 seconds for promotional SMS)
DND Bypass
Delivered to all mobile numbers regardless of Do Not Disturb (DND) registration status
24/7 Availability
No time restrictions - can be sent anytime including nights, weekends, and holidays
Higher Deliverability
98%+ success rate using direct Tier-1 telecom operator connections
TRAI Compliant
Fully compliant with Indian telecom regulations for transactional messaging
Transactional SMS is essential for any business that requires real-time customer communication for account security, service updates, or operational alerts. In India, over 2 billion transactional SMS are sent monthly across banking, e-commerce, healthcare, logistics, and SaaS sectors.
Transactional SMS API Features Built for Mission-Critical Messaging
OTP SMS API for Authentication
Send secure one-time passwords for login verification, two-factor authentication (2FA), password reset, and transaction approval with guaranteed sub-5-second delivery.
Instant Transactional SMS Delivery
Critical alerts, order confirmations, and notifications delivered within seconds using priority transactional routes with automatic retry logic for failed messages.
DLT-Compliant SMS API
Fully compliant with TRAI DLT (Distributed Ledger Technology) regulations including mandatory sender ID registration, template approval, and consent management.
Real-Time Delivery Reports & Webhooks
Track every message with granular delivery status: sent, delivered, failed, or expired. Get instant notifications via webhooks or query via API.
REST API with Multiple Languages
Simple HTTP REST API with official SDKs for Python, PHP, Node.js, Java, C#, and Ruby. Send SMS with just 3 lines of code.
Enterprise-Grade Infrastructure
Built on redundant carrier-grade routes with automatic failover, load balancing across 10+ direct operator connections, and guaranteed 99.9% API uptime.
Affordable SMS API Pricing in India
Pay only for the SMS you send. No hidden charges. Plans starting at just ₹0.11 per SMS.
Transactional SMS vs Promotional SMS: Key Differences
| Feature | Transactional SMS | Promotional SMS |
|---|---|---|
| Purpose | OTPs, alerts, notifications | Marketing, offers, campaigns |
| DND delivery | ✅Yes - delivers to all | ❌No - blocked by DND |
| Delivery time | ✅2-5 seconds priority | ⏱️5-30 seconds standard |
| Sending hours | ✅24/7 anytime | ❌9 AM - 9 PM only |
| Sender ID type | 6-char alphanumeric (e.g., VERIFY) | 6-char alphanumeric |
| DLT requirement | ✅Required | ✅Required |
| Cost per SMS | ₹0.11-0.14 | ₹0.10-0.15 |
| Best for | OTPs, banking alerts, order confirmations | Promotional campaigns, offers |
| Max message length | 160 chars (or 3-part concatenated) | 160 chars (or 3-part concatenated) |
Transactional SMS API Features & Capabilities
🔐1. OTP SMS API for Secure Authentication
Send one-time passwords for login verification, two-factor authentication (2FA), password reset, and transaction approval with guaranteed sub-5-second delivery.
OTP Features:
Real Performance Data: Our fintech clients send 500K+ OTPs daily with 99.2% delivery rate and average 2.8-second delivery time across all Indian telecom operators (Jio, Airtel, Vi, BSNL).
📱2. Transaction Alert SMS API
Send instant alerts for financial transactions, order confirmations, payment receipts, and account activities with real-time delivery status tracking.
Use Cases:
Banking:
Debit/credit alerts, account balance updates, fund transfers
E-commerce:
Order placed, shipped, out for delivery, delivered
Payments:
UPI transaction success/failure, wallet top-up, refund processed
Subscriptions:
Renewal reminders, payment due, subscription activated
✅3. DLT-Compliant SMS API (TRAI Regulations)
100% compliant with TRAI's Distributed Ledger Technology (DLT) platform for commercial messaging in India. We handle the complexity so you can focus on your business.
DLT Compliance Features:
📊4. Real-Time Delivery Reports & Webhooks
Track every single message with granular delivery status updates and instant webhook notifications for critical events.
Available Status Codes:
Detailed Metrics:
💻5. Developer-Friendly REST API
Simple HTTP REST API with comprehensive documentation, interactive API explorer, and official SDKs for all major programming languages.
API Capabilities:
Official SDKs Available:
Integration Time: 15-30 minutes with complete documentation, code examples, and Postman collection.
🏢6. Enterprise-Grade Infrastructure
Built on carrier-grade infrastructure with redundant routing, automatic failover, and guaranteed 99.9% API uptime SLA.
Infrastructure Features:
Transactional SMS API Use Cases by Industry
🏦Banking & Financial Services
Critical account security and transaction notifications:
- •OTP for net banking login and mobile app authentication
- •Debit/credit card transaction alerts (real-time)
- •Fund transfer confirmations (NEFT/RTGS/IMPS/UPI)
- •Account balance alerts and low balance warnings
- •Loan EMI payment reminders and due date alerts
- •Credit card payment due reminders
- •Suspicious activity alerts and fraud detection
- •ATM withdrawal notifications
- •Cheque clearance status updates
💳Fintech & Digital Payments
Secure authentication and payment alerts:
- •Wallet top-up confirmation and balance updates
- •Peer-to-peer payment transaction alerts
- •UPI transaction success/failure notifications
- •Investment app login OTP and verification
- •Buy-now-pay-later (BNPL) approval confirmations
- •Cryptocurrency transaction alerts
- •Insurance premium payment confirmations
- •Mutual fund SIP debit notifications
🛒E-commerce & Retail
Order lifecycle and customer service alerts:
- •User registration and login OTP
- •Order confirmation with order ID and estimated delivery
- •Payment confirmation and invoice generation
- •Order shipped with tracking number
- •Out for delivery with expected time window
- •Order delivered confirmation
- •Return/refund initiated and processed alerts
- •Delivery rescheduling notifications
- •Cash on delivery (COD) reminders
🏥Healthcare & Telemedicine
Patient engagement and medical alerts:
- •Appointment booking confirmation with date/time
- •Appointment reminder (24 hours before)
- •Doctor consultation rescheduling alerts
- •Lab test report ready notifications
- •Prescription refill reminders
- •Vaccination schedule reminders
- •Medicine delivery tracking updates
- •Emergency medical alerts
- •Health insurance claim status updates
📚Education & EdTech
Student and parent communication:
- •Student login OTP for learning portals
- •Course enrollment confirmation
- •Live class/webinar starting in 15 minutes
- •Assignment submission confirmation
- •Exam schedule and admit card alerts
- •Result declaration notifications
- •Fee payment confirmation and receipt
- •Attendance alerts to parents
- •Certificate generation completion
✈️Travel & Hospitality
Booking confirmations and travel updates:
- •Flight booking confirmation with PNR
- •Flight delay/cancellation alerts
- •Web check-in reminder (24 hours before)
- •Hotel reservation confirmation
- •Check-in/check-out reminders
- •Cab booking and driver assignment
- •Bus/train ticket confirmation
- •Visa application status updates
- •Travel insurance confirmation
📦Logistics & Delivery
Shipment tracking and delivery updates:
- •Shipment picked up from sender
- •In-transit status with location updates
- •Reached destination city/hub
- •Out for delivery with delivery partner details
- •Delivery attempt failed (with reason)
- •Successfully delivered with proof
- •Return to origin updates
- •Proof of delivery (POD) notifications
⚙️SaaS & Technology Platforms
User authentication and system alerts:
- •User registration and email verification OTP
- •Login OTP for two-factor authentication
- •Password reset OTP and confirmation
- •Subscription activated/renewed alerts
- •Payment failure and retry notifications
- •Account security alerts (new device login)
- •Feature unlock or upgrade confirmation
- •System maintenance and downtime alerts
- •API usage limit warnings
How to Integrate Transactional SMS API (Step-by-Step)
1Register on DLT Platform
(2-3 business days)
- •Register your business entity on TRAI DLT platform (Vilpower/Airtel/Jio/Vi DLT)
- •Upload business documents (GST, PAN, incorporation certificate)
- •Get Entity ID after approval
2Create Sender ID (Header)
- •Apply for 6-character alphanumeric sender ID (e.g., CONNEX)
- •Submit trademark/brand ownership proof
- •Wait for approval (1-2 business days)
3Register Message Templates
- •Create message templates for each type of SMS (OTP, alerts, etc.)
- •Submit templates for approval on DLT
- •Get Template ID after approval
4Get API Credentials
- •Sign up on ConnexBetter dashboard
- •Add your Entity ID, Sender ID, and Template IDs
- •Generate API Key and Secret
5Send Your First SMS
Use our REST API to send SMS in 3 lines of code:
Example (cURL):
curl -X POST https://api.connexbetter.com/v1/sms/send \
-H "Authorization: Bearer YOUR_API_KEY" \
-H "Content-Type: application/json" \
-d '{
"to":"919876543210",
"message":"Your OTP is 123456",
"sender_id":"CONNEX",
"template_id":"1234567890123456789"
}'6Track Delivery Status
- •Check delivery status via dashboard or API
- •Set up webhooks for real-time status updates
- •Download delivery reports (CSV/Excel)
Compliance, Security & Certifications
✅Regulatory Compliance
- ✓TRAI DLT platform registered and certified
- ✓Telecom Commercial Communications Customer Preference Regulations, 2018 compliant
- ✓TCCCPR 2018 amendments compliant
- ✓Data Protection and Privacy Act compliant
🛡️Security Certifications
- ✓ISO 27001:2013 Information Security Management
- ✓PCI-DSS Level 1 certified for payment data
- ✓SOC 2 Type II certified
- ✓GDPR compliant data handling
🔒Security Features
- ✓End-to-end TLS 1.3 encryption
- ✓API key rotation and expiry management
- ✓IP whitelisting for API access
- ✓Rate limiting and DDoS protection
- ✓Audit logs and activity monitoring
- ✓Two-factor authentication for dashboard
How to choose an SMS provider
Here are the key factors you should consider when choosing an SMS provider.
Easily integrate SMS API with your existing tech stack
Frequently Asked Questions
Find quick answers to your questions about our API services, integration, and support.
Contact Our Support Team
A transactional SMS API is a programmable interface that allows businesses to send automated, time-critical messages like OTPs, alerts, and notifications via HTTP requests. Unlike promotional SMS used for marketing, transactional SMS bypasses DND restrictions, delivers 24/7 using priority routes (2-5 seconds vs 5-30 seconds), and is designed for essential business communications like account security, order updates, and service alerts.
Yes, absolutely. Transactional SMS including OTPs, banking alerts, order confirmations, and service notifications are delivered to ALL mobile numbers regardless of DND (Do Not Disturb) status. This is permitted under TRAI regulations because transactional messages contain critical, non-promotional information essential for business operations and customer service. Only promotional/marketing SMS are blocked by DND.
OTP messages are delivered within 2-5 seconds on average using our priority transactional routes. 95% of OTPs are delivered within 3 seconds, and 99% within 5 seconds. We use direct Tier-1 operator connections (Jio, Airtel, Vi, BSNL) with automatic failover to ensure fastest possible delivery. Real-time delivery tracking is available via webhooks or API.
Yes, 100%. Our SMS API is fully compliant with TRAI''s Distributed Ledger Technology (DLT) platform requirements. We provide Entity ID registration assistance, Sender ID approval support, template creation guidance, and automatic validation of all messages against DLT-approved templates before sending. All SMS are sent with registered Entity IDs, Sender IDs, and Template IDs as mandated by TRAI.
Transactional SMS is for service-related messages (OTP, alerts, confirmations) and can be sent 24/7 to all numbers including DND with 2-5 second delivery. Promotional SMS is for marketing messages (offers, campaigns) and can only be sent 9 AM - 9 PM to non-DND numbers with 5-30 second delivery. Transactional costs more (?0.20-0.28) but is essential for critical communications. Both require DLT compliance.