01 · Definition
What is a DLT header?
A DLT Header is the sender ID that a business, the Principal Entity, registers on India's DLT platform and uses on its commercial SMS. It is what recipients see in their message list instead of a phone number, and under TRAI's TCCCPR 2018 no commercial SMS may be sent from a header that is not registered to the sending entity.
Headers are registered by message category, and the category decides the format: a brand-like code for service and transactional traffic follows different rules from a header for promotional traffic, so check your operator portal's current rules before applying. Each header is then linked to the DLT Content Template records it may send, and DLT Scrubbing checks the header, the template ID and the PE ID together on every message.
On the handset, the operator adds a two-letter prefix identifying the originating network and service area, and headers now carry a category suffix: -T for transactional, -S for service, -P for promotional and -G for government. A service message from the header NGPBNK might therefore show as AD-NGPBNK-S. Sender ID is the general idea worldwide; the DLT header is India's version, registered to one entity and bound to its categories and templates.
Key takeaways
- A DLT header is the sender ID a principal entity registers on DLT: the name recipients see on its commercial SMS.
- A header's format depends on its message category, and each header is linked to the content templates it may send.
- Phones show a two-letter network-and-circle prefix before the header, and headers now carry a category suffix: -T, -S, -P or -G.
- A template sent from a header it is not linked to fails DLT scrubbing, so the SMS is never delivered.
- Sender ID is the global concept; the DLT header is India's registered, category-bound version of it.
02 · Specifications
A DLT header: key facts and limits
| Registered by | The principal entity, on an operator DLT portal |
|---|---|
| Format | Depends on the message category; check your portal |
| Display prefix | Two letters: originating network and service area |
| Category suffix | -T, -S, -P or -G after the header |
| Linked to | The content templates it may send |
| Checked at | DLT scrubbing, with the PE ID and template ID |
| Global equivalent | Sender ID |
03 · Operation
How does a DLT header work?
Choose the header
Pick a code that clearly relates to the brand or entity name. Portals may ask for proof, such as a trademark certificate or an authorisation letter, when the link is not obvious.
Select the category
Register the header for promotional traffic or for service and transactional traffic. The category fixes the header's format and which templates it can carry.
Apply on the DLT portal
The principal entity applies on its operator's DLT portal. Once approved, the header is visible to every operator through DLT.
Link templates to the header
When registering each content template, link it to the header or headers that will send it. One template can be linked to several headers of the right category.
Send with header, template and PE ID
Every submission names the header. Scrubbing checks that it belongs to the PE and is linked to the template ID, and the operator adds the prefix and suffix on the way to the phone.
04 · Rationale
Why does a DLT header matter?
The header is a brand's face in the inbox and the first thing a cautious customer checks before trusting an OTP or a payment alert. Getting it registered, linked to the right templates and kept consistent across services decides whether messages reach people at all, and whether they recognise them when they do. With the category suffix on display, a promotional message can no longer pass as a service alert, so choosing the right category for each header matters for both delivery and trust.
05 · Code samples
A DLT header in code
// Refuse a send whose header is not linked to the template on DLT.// Mirror your DLT registrations here (IDs are placeholders).const templates = {"{TEMPLATE_ID_OTP}": { category: "transactional", headers: ["NGPBNK"] },"{TEMPLATE_ID_OFFER}": { category: "promotional", headers: ["{PROMO_HEADER}"] },};export function checkHeader(templateId, header) {const t = templates[templateId];if (!t) throw new Error("Unknown DLT template ID " + templateId);if (!t.headers.includes(header)) {throw new Error("Header " + header + " is not linked to template " + templateId);}return t.category; // pass it on for routing and reporting}// What a recipient sees: operator prefix, your header, category suffix.// Display formats vary by handset, e.g. "AD-NGPBNK-S".export function parseDisplayedSender(s) {const m = /^([A-Z]{2})[- ]([A-Z0-9]+)-([TSPG])$/.exec(s);return m ? { prefix: m[1], header: m[2], suffix: m[3] } : null;}
Scrubbing would reject the mismatch anyway; catching it before submission saves the failed sends and shows the error to the person who caused it.
06Playground
A working model of DLT Header. Use its controls to replay it step by step.
Type a header and see what the recipient's phone shows
Close to the limit: only 0 left. Keep headroom if part of this text is filled in at send time.
Operator portals commonly take a brand-like header of up to six characters for service and transactional traffic; promotional headers follow a different format. Confirm the rule on your portal.
Close to the limit: only 0 left. Keep headroom if part of this text is filled in at send time.
The operator adds a two-letter network-and-circle prefix and the category suffix. Together with the header they fit the 11-character alphanumeric sender field.
Close to the limit: only 0 left. Keep headroom if part of this text is filled in at send time.
Many countries accept alphanumeric sender IDs of up to 11 characters with no DLT step. In India only a registered header may be used.
Counted in Unicode code points, so an emoji, ₹ or an accented letter counts as one character.
07 · Cautions
Common mistakes with a DLT header
A header unrelated to the brand
Portals reject or query headers that do not resemble the entity's name. Pick something recognisable and keep the supporting documents ready.
One header for everything
Alerts and offers from the same sender teach customers to ignore both. Keep promotional traffic on its own header and category.
Forgetting to link new templates
A new template that is not linked to the sending header fails scrubbing even though both are approved. Link every template to each header that will use it.
A new header for every campaign
Customers trust a stable sender. Dozens of headers dilute recognition and multiply registration work, so reuse a small set per category.
Expecting to choose the suffix
The operator adds -T, -S, -P or -G from the registered category. The only way to change it is to register the traffic under the right category.
08 · Worked example: A Nagpur co-operative bank's two headers
Example: A Nagpur co-operative bank's two headers
A Nagpur co-operative bank registers one header for transaction OTPs and account alerts and links it only to its transactional and service-implicit templates; its loan offers go out from a separate promotional header. When a branch manager tries to send a festive loan offer from the alerts header, the offer template is not linked to it and scrubbing rejects the messages. That is exactly what the bank wants: customers have learned that messages from the alerts header, ending -T or -S, never carry a sales pitch, which makes a fraudulent look-alike easier to spot.
09 · Questions and answers
DLT Header FAQs
- What is a header in DLT?
- It is the sender ID a business registers on India's DLT platform for its commercial SMS, the name recipients see instead of a phone number. Each header belongs to one principal entity and is linked to the templates it may send.
- What do -S, -T, -P and -G mean at the end of an SMS sender?
- They are category suffixes that operators add to commercial SMS headers: -T for transactional, -S for service, -P for promotional and -G for government messages. They tell recipients what kind of message it is before they open it.
- Can I send promotional SMS from my service header?
- No. Promotional templates must go out from a header registered for promotional traffic. Scrubbing rejects a template sent from a header it is not linked to, and the suffix shows recipients which kind of message it is.
- Is a DLT header the same as a sender ID?
- It is India's registered form of one. Sender ID is the general term for the originator a recipient sees; a DLT header is a sender ID registered on DLT to one principal entity and bound to its categories and templates.
10 · Recommended practice
Best practices for a DLT header
- Use the same recognisable brand code across categories where the formats allow, so customers learn one name.
- Tell customers on your website and in your app which header your OTPs come from.
- Keep a register mapping each header to its category and linked template IDs.
- Review headers once a year and retire the ones nothing sends from.