What is a sender ID?
When a text lands on a phone, the label at the top — whether it's a brand name or a number — is the sender ID. It's the SMS equivalent of the "from" line in an email. A recognisable sender ID is often the difference between a message that gets opened and one that gets ignored as spam.
There are two main types, and choosing the right one depends on your goal and your country's rules.
Alphanumeric vs numeric sender IDs
Alphanumeric sender ID | Numeric sender ID | |
|---|---|---|
Looks like | A brand name, e.g. "Helo Ai" | A phone number or short code |
Length | Up to 11 characters | Varies by number type |
Two-way replies? | No — one-way only | Yes |
Best for | Branded alerts, OTPs, notifications | Conversations and support |
Availability | Supported in many countries; not in the US (uses 10DLC/short codes) | Widely supported |
An alphanumeric sender ID is ideal for one-way messages like transactional alerts and OTPs, where you want your brand front and centre. A numeric sender ID is needed when customers must be able to reply — see Two-Way Messaging.
How sender IDs work in India (DLT headers)
In India, a sender ID is called a header, and it must be registered on the DLT (Distributed Ledger Technology) platform before you can send business SMS. A few essentials:
- Headers are typically 6 characters (alphanumeric) and case-sensitive, registered in capitals.
- Each header is tied to a message category — Promotional, Transactional, Service, or Other.
- Headers must be linked to registered templates.
- Registration prevents duplication and fraud, so only your brand can send under your header.
Helo.ai's DLT Management service handles header and template registration so your messages actually get delivered.
Benefits of a branded sender ID
- Brand recognition: recipients instantly see who's messaging.
- Higher open and response rates: trusted names get opened.
- Reduced spam flagging: carriers are less likely to block recognised senders.
- Professional appearance: consistent branding across every message.
Sender ID use cases
- OTP and verification messages
- Transactional alerts (orders, payments, shipping)
- Promotional campaigns
- Appointment and service reminders
Related on Helo.ai: SMS · DLT Management · DLT (glossary) · Short Code vs Long Code
Frequently asked questions
What is a sender ID in SMS?
It's the name or number shown as the sender of a text message — either a branded alphanumeric string or a numeric code — that tells recipients who the message is from.
What is the difference between alphanumeric and numeric sender IDs?
Alphanumeric sender IDs show a brand name and are one-way only. Numeric sender IDs use a phone number or code and support two-way replies.
Do I need to register a sender ID in India?
Yes. In India, sender IDs (headers) must be registered on the DLT platform and linked to approved templates before you can send business SMS.
Can recipients reply to an alphanumeric sender ID?
No. Alphanumeric sender IDs are for one-way messaging. To receive replies, use a numeric long or short code.