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The definitive technical reference for integrating a transactional SMS API in India — covering TRAI DLT compliance, REST endpoint structure, OTP delivery benchmarks, error handling patterns, webhook setup, multi-language SDK examples, and a frank comparison of every major provider. Written by engineers who run SMS infrastructure, for engineers who build on it. Table of Contents What Is a Transactional SMS API? Transactional vs Promotional SMS — Technical Differences TRAI DLT

Every time a user logs into your app, completes a payment, or receives a delivery update in India, an SMS Gateway API is doing the work invisibly in the background. But not all SMS Gateway APIs are built the same — and in India, the gap between a well-integrated API and a poorly chosen one shows up as OTP failures, blocked promotional messages, DLT rejections, and delivery delays that cost you conversions you will never see in your analytics. This is the complete developer gu

Bulk messaging is one of the most widely used communication tools in Indian business — and one of the most poorly measured. Most businesses track exactly one number: how many messages were sent. A few track delivery rate. Almost none track the full chain from message dispatch to actual business outcome — completed purchases, confirmed appointments, redeemed offers, or recovered abandoned transactions. The result is that bulk messaging campaigns run on assumption rather than

Transactional SMS Transactional SMS in India is the category of commercial SMS that carries critical, non-marketing information to customers — order confirmations, appointment reminders, bank transaction alerts, OTP authentication codes, and delivery notifications — delivered 24 hours a day, 7 days a week, to every mobile number in India including DND-registered ones. Unlike promotional SMS, which is subject to TRAI's 10 AM–9 PM time window and blocked on the 28 crore DND-reg

SMS Types India's SMS ecosystem is unlike any other in the world. Under TRAI's mandatory DLT (Distributed Ledger Technology) framework, every commercial SMS sent in India falls into one of five legally defined categories — each with its own delivery rules, sender ID format, time restrictions, DND permissions, and pricing. Choosing the wrong SMS type in India does not just affect your campaign performance — it gets your messages blocked at the operator level before they reach

Generic bulk SMS is dead. Customers ignore "Dear Customer" — they respond to "Hi Priya." Techto Networks' personalized SMS service lets you send thousands of individually customized messages simultaneously, with each recipient's name, purchase amount, appointment date, location, discount code, or any other variable pulled directly from your contact list or CRM. Every message feels handcrafted. Every send is delivered at bulk speed and bulk pricing — from ₹0.10 per SMS. This i