Quick Answer
An OTP SMS provider sends one-time passwords by SMS to verify users at sign-up, login, payment or password reset. In India an OTP is transactional: it carries a -T header suffix, goes out within 30 minutes of the user's action, reaches DND numbers 24/7 and must match a DLT template with a {#numeric#} variable. SMSGatewayHub delivers OTPs in 2-6 seconds on Pay As You Go pricing.
Which DLT category does an OTP SMS use?
Operators now append a suffix to every sender ID, so customers see the message type, for example AB-ABCDEF-T. OTPs belong in the transactional category; anything else slows them down or gets them blocked.
| Message | Category & suffix | Why | DND & timing |
|---|
| Login, sign-up and app verification OTP | Transactional -T | Sent in response to an action the user just took, within 30 minutes of it. | Reaches DND numbers, 24/7 |
| Payment, UPI and card transaction OTP | Transactional -T | Confirms a transaction the customer initiated; TRAI lists bank and app OTPs as transactional. | Reaches DND numbers, 24/7 |
| Password reset and new-device login OTP | Transactional -T | Triggered by the user's own reset or login request. | Reaches DND numbers, 24/7 |
| Security alert after a login (no code) | Service -S | An update about an account the customer already holds, not a response to a fresh request. | Reaches DND numbers, no promotional content |
| OTP with an offer or coupon line added | Promotional -P | Any marketing content turns the whole message promotional. | DND filtering, consent and promotional time window apply |
Keep OTP templates strictly free of offers. Compare categories on transactional SMS and service explicit vs service implicit SMS, and see how suffixes appear on SMS sender IDs.
What changed for OTP SMS under the latest TRAI and DLT rules?
Four rules now decide whether an OTP is delivered in seconds or rejected at DLT scrubbing.
-T suffix on every OTP
Operators append -T to transactional headers, so users can tell a genuine OTP from marketing. Your OTP templates must be registered as transactional or they will be labelled and treated as something else.
30-minute transactional window
A message counts as transactional only when it is sent within 30 minutes of the customer's own transaction. OTPs fired by the API at the moment of login or payment meet this naturally.
Typed variables, not {#var#}
The code must sit in a {#numeric#} tag and other values in {#alphanumeric#}, {#url#} or {#cbn#}. See converted OTP formats on our DLT sample templates page.
Whitelisted links and numbers only
Any URL or callback number inside an OTP must be registered as a CTA on DLT. Unregistered links and public URL shorteners are blocked, so most OTP templates carry no link at all.
Why SMSGatewayHub
Why choose SMSGatewayHub over other OTP SMS providers?
An OTP that arrives late is a lost sign-up or a failed payment. Here is what sets SMSGatewayHub apart when you compare OTP SMS providers in India.
Multi-operator routing with failover
OTP traffic is routed across operators with automatic failover, giving 2-6 second typical delivery and a 99.9% uptime SLA, even at peak login hours.
Auto-read and silent verification
OTP formats that phones can auto-detect, plus REST APIs and widgets that drop OTP verification into apps and websites without heavy coding.
Certified security
ISO 27001, ISO 9001:2015, SOC 2 and VAPT tested, with masked OTP content in reports. Trust Center
Fallback to voice, WhatsApp or missed call
If SMS is slow on a user's network, retry the code by voice or WhatsApp, or verify with a missed call, from the same account.
Trusted since 2009
10,000+ registered businesses and 2,000+ enterprise clients, with 24/7 support and a toll-free sales line, 1800 102 1822.
| Question to ask any OTP SMS provider | SMSGatewayHub |
|---|
| Am I charged for OTPs that never arrive? | No. You pay only for delivered SMS. |
| What is your typical OTP delivery time? | 2-6 seconds in typical conditions, with operator failover. |
| Are delivery reports real operator reports? | Yes, live operator delivery reports in the panel and API. See delivery reports |
| Who fixes my OTP templates for the typed-variable rule? | Our DLT team converts and re-registers them. DLT priority support |
| Can I fall back to another channel if SMS fails? | Yes: voice OTP, WhatsApp OTP or missed call verification. |
| Can I test before I buy? | Yes, start with 1,000 free SMS credits. Create a free account |
Switching providers? See our MSG91 alternative page or read why OTP SMS is not received and how to fix it.
OTP SMS use cases by industry
Each card links to a dedicated industry page with message samples and DLT tips.
Banks, NBFCs & fintech
Net banking login, card and UPI transaction OTPs, loan e-sign and KYC verification. Bulk SMS for banks & NBFCs
Hospitals & clinics
Patient portal logins, appointment booking verification and report access codes. Bulk SMS for hospitals
Schools & EdTech
Student and parent app logins, exam portal access and fee payment OTPs. Bulk SMS for education
Logistics & courier
Delivery handover codes, driver app logins and proof-of-delivery verification. Bulk SMS for logistics
DLT-compliant OTP SMS template examples
The OTP itself goes in a {#numeric#} tag. State the purpose, validity and a do-not-share line; skip links unless they are whitelisted CTAs.
| Message (what the user sees) | DLT template (typed-variable format) | Suffix |
|---|
| 482913 is your OTP to log in to ABC App. Valid for 10 minutes. Do not share it with anyone. - ABC | {#numeric#} is your OTP to log in to ABC App. Valid for {#numeric#} minutes. Do not share it with anyone. - ABC | -T |
| Use OTP 715204 to verify your mobile number on ABC Store. Never share this code. - ABC Store | Use OTP {#numeric#} to verify your mobile number on ABC Store. Never share this code. - ABC Store | -T |
| OTP 390176 for payment of Rs.2499 at ABC Store. Valid for 5 minutes. Do not share. - ABC Bank | OTP {#numeric#} for payment of Rs.{#numeric#} at {#alphanumeric#}. Valid for {#numeric#} minutes. Do not share. - ABC Bank | -T |
| 628451 is your code to reset your ABC App password. If you did not request this, ignore this SMS. - ABC | {#numeric#} is your code to reset your ABC App password. If you did not request this, ignore this SMS. - ABC | -T |
| <#> 573920 is your ABC App verification code. FA+9qCX9VSu | <#> {#numeric#} is your ABC App verification code. {#alphanumeric#} | -T |
The last row shows an auto-read format, where the trailing value is your app's hash. More formats on the DLT template registration process page and in the blog on TRAI's mandatory variable tagging update.
How to start sending OTP SMS
Register on DLT
Register your business as a Principal Entity on an operator DLT portal. Our team guides you through DLT registration.
Get a transactional header
Register a 6-character alphabetic sender ID under the transactional category for your OTPs.
Register OTP templates
Submit each OTP template with a {#numeric#} tag for the code and no promotional wording.
Integrate the OTP API
Map template IDs in your panel and call the HTTPS API, HTTP API or SMPP from your login, sign-up and payment flows.
Monitor and add fallback
Track every OTP in live delivery reports and add voice or missed call fallback for hard-to-reach numbers.
OTP security best practices
Fast delivery is half the job; these habits keep your OTP flow safe from abuse and fraud.
- Keep OTPs short-lived: set a validity of a few minutes and say it in the message.
- Limit verification attempts and resend requests per number to stop brute-force and SMS bombing.
- Always include a do-not-share warning and the purpose of the code. Keep OTPs out of the spam folder.
- Generate and check codes on your server; never return the OTP in an API response to the app.
- Restrict API access with keys and IP whitelisting, and mask OTP content in reports.
- Add a fallback channel such as voice OTP or missed call verification for numbers that repeatedly fail.
OTP SMS resource map
Everything related to OTP SMS on SMSGatewayHub, grouped by what you need to do next.
SMS OTP vs missed call OTP vs WhatsApp OTP: which do you need?
Use SMS OTP as your default: it works on every phone without an app or data connection, and transactional -T routes reach DND numbers at any hour. Use missed call OTP when you only need to confirm that a user owns a number, such as sign-ups and COD confirmations, and want to avoid typing and SMS delays. Use WhatsApp or voice OTP as a fallback when a user has opted in or SMS keeps failing on their network.
Need OTPs across several channels with one enterprise API? See bulk SMS messaging for OTP. For implementation detail, read the OTP SMS API integration guide for India and SMS API with WhatsApp OTP fallback.
Frequently Asked Questions
What is an OTP SMS provider?
An OTP SMS provider sends one-time passwords by SMS so a business can verify a user during sign-up, login, payment or password reset. SMSGatewayHub provides OTP SMS over HTTP, HTTPS and SMPP APIs on transactional routes, with live delivery reports for every code.
Is OTP SMS transactional or service SMS in India?
OTPs are transactional. TRAI defines a transactional message as one sent in response to a transaction the customer initiated, within 30 minutes of it, and lists OTPs from banks, e-commerce and app logins as examples. They carry a -T header suffix.
Can OTP SMS be delivered to DND numbers?
Yes. Transactional OTP messages reach all Indian numbers, including those on the DND list, 24/7. They lose this if any promotional content is added, because the message then becomes promotional.
How fast does SMSGatewayHub deliver OTP SMS?
SMSGatewayHub delivers OTP SMS in 2-6 seconds in typical conditions, using multi-operator routing with automatic failover and a 99.9% uptime SLA. Live delivery reports show the status of every code.
How do I register an OTP template on DLT?
Register your entity and a 6-character alphabetic header on a DLT portal, then submit the OTP template under the transactional category with the code in a {#numeric#} tag. Any link or callback number must also be whitelisted as a CTA. SMSGatewayHub's DLT team can help convert and register templates.
What does OTP SMS cost with SMSGatewayHub?
SMSGatewayHub uses Pay As You Go pricing: you buy credits as needed and pay only for delivered SMS; exact rates depend on volume and route, see https://www.smsgatewayhub.com/pricing or talk to sales on 1800 102 1822.
What if a user does not receive the OTP SMS?
Check the delivery report first, then common causes such as a template mismatch, a wrong or ported number, or weak network coverage. SMSGatewayHub lets you retry the code by voice or WhatsApp, or switch to missed call verification, from the same account.
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