When you set up business messaging in India, you choose how your messages identify themselves and how customers can reply. The three options people confuse most are short codes, long codes and sender IDs. They serve different purposes, carry different costs and fit different use cases. This guide explains what each one is, when to use it, how the DLT framework applies and gives concrete Indian examples so you can pick with confidence.
Sender ID, also called a header
A sender ID is the six-character alphanumeric code that appears as the sender of a bulk SMS, for example a header like GURUMS or HDFCBK. It is the most common identity for business SMS in India. Sender IDs are used for one-way, outbound messages: offers, alerts, OTPs, confirmations and reminders. Customers cannot reply to a sender ID, because it is a name rather than a number.
Under DLT, every sender ID, known as a header, must be registered against your entity before you can send. Headers are mapped to a category, transactional or promotional, and your approved templates are linked to them. This is why a header is the foundation of any compliant bulk SMS setup. If you only need to push messages out and do not expect replies, a registered sender ID is the right and most economical choice.
Long code
A long code is a standard ten-digit mobile number, the same format as any personal Indian number, dedicated to your business for two-way messaging. Customers can both receive messages from it and reply to it, and those replies land back with you. Long codes suit conversational use cases: capturing leads who text a keyword, running feedback and survey flows, or letting customers opt in by replying. Because it is an ordinary number, the cost is modest, but throughput is lower than a short code, so a long code is not ideal for very high inbound volumes.
A typical pattern is to advertise a line such as text JOIN to 90XXXXXXXX. Replies are routed to your platform, where you parse the keyword and trigger the right workflow. Long codes are a good middle ground when you need interactivity without the premium of a short code.
Short code
A short code is a five or six-digit number, for example 56767, that is short, memorable and easy to print on packaging, posters and TV ads. Short codes are built for high-volume two-way messaging and premium campaigns. They handle far greater inbound throughput than long codes, which makes them suitable for large contests, nationwide voting, banking keyword services and any campaign expecting heavy reply traffic. They are the most premium of the three options and involve a setup and rental commitment, but for brands running mass-market interactive campaigns the memorability and capacity are worth it.
Short codes can be shared or dedicated. A dedicated short code is reserved for one brand, giving full control over keywords, while a shared short code splits keywords across several businesses at lower cost.
How DLT applies to all three
Whichever identifier you use, the DLT framework governs it. Sender IDs are registered as headers tied to your entity and category. For long codes and short codes used to send outbound commercial messages, the same template and consent rules apply, and inbound keyword services must be set up in line with TRAI norms. DND scrubbing and the 9 AM to 9 PM promotional window apply to promotional traffic regardless of the identifier. In short, the choice of identifier changes how customers see and reply to you, but it does not exempt any message from compliance.
Choosing the right option
- Pick a sender ID when you only send outbound messages and do not need replies. This covers most OTPs, alerts and promotional broadcasts, and it is the standard choice.
- Pick a long code when you want two-way conversations at moderate volume, such as lead capture, feedback or opt-in by reply.
- Pick a short code when you run high-volume interactive campaigns and want a memorable number on mass advertising.
Many businesses combine them. You might send OTPs and offers from a sender ID, capture leads on a long code, and run a national contest on a short code. Our full range of services supports all three, and our team helps you register each correctly.
Examples by use case
- Bank OTP: sender ID header, transactional route, no reply needed. Best served by a dedicated OTP SMS route.
- Retail offer blast: sender ID header, promotional route, sent within the permitted window.
- Insurance lead capture: long code, customer texts a keyword to express interest.
- TV show voting: short code, millions of inbound votes over a short period.
Where WhatsApp fits
For richer two-way conversations with media, buttons and a verified business profile, many brands now layer the WhatsApp channel on top of SMS. SMS identifiers handle reach and reliability, while WhatsApp handles depth of conversation. Choosing the right SMS identifier and pairing it with WhatsApp where appropriate gives you the best of both.
Frequently Asked Questions
Can customers reply to a sender ID?
No. A sender ID is an alphanumeric name, not a number, so it is one-way only. If you need replies, use a long code or a short code instead.
What is the difference between a long code and a short code?
A long code is a regular ten-digit mobile number for moderate two-way messaging, while a short code is a five or six-digit number built for high-volume, memorable interactive campaigns at a premium.
Do short codes and long codes need DLT registration?
Yes. Any commercial outbound message in India is governed by DLT, including template and consent rules, regardless of whether it goes through a sender ID, long code or short code.
Which option is most economical for OTPs and alerts?
A registered sender ID on a transactional route is the standard and most economical choice for OTPs and alerts, since these are one-way and require no reply.
Not sure which identifier fits your campaigns? The Guru SMS team will assess your use case, recommend the right mix of sender ID, long code or short code, and handle the DLT registration. Visit our contact page or call +91-9853084604 to talk it through.