# What is a sender ID?

> A sender ID is the 'from' identity a recipient sees on an A2P SMS. It can be an alphanumeric string (up to 11 GSM-7 characters, typically a brand name), a numeric long code, or a short code. Alphanumeric sender IDs let brands show a recognisable name instead of a number, but most countries require them to be pre-registered with the regulator or operator before traffic will deliver.

- Canonical URL: https://www.broadnet.me/answers/what-is-sender-id
- Language: en
- Last reviewed: 2026-07-22
- Publisher: BroadNet (https://www.broadnet.me)

## Alphanumeric vs numeric vs short code

Alphanumeric IDs are one-way (the recipient can't reply) and ideal for OTPs and notifications. Long codes are two-way and support conversational replies. Short codes offer the highest throughput for large campaigns. Some markets — notably the United States — do not allow alphanumeric IDs at all and require 10DLC, toll-free, or short codes instead. See /answers/what-is-short-code-vs-long-code.

## Registration and spoofing

Sender-ID registration is per country and often per operator; unregistered IDs are dropped by the operator's SMS firewall. Because the SMS 'from' field is trivially spoofable on grey routes, sender-ID spoofing is a common smishing vector — defended by firewalls, registration enforcement, and verified-sender channels like RCS Business Messaging. See /answers/sender-id-registration-uae-tdra and /answers/what-is-sender-id-spoofing.

## Related

- [All answers](https://www.broadnet.me/answers)
- [Glossary](https://www.broadnet.me/answers)
- [What is an alphanumeric sender ID?](https://www.broadnet.me/answers/what-is-alphanumeric-sender-id)
- [Short code vs long code — when to use each](https://www.broadnet.me/answers/what-is-short-code-vs-long-code)
- [Sender ID registration in the UAE — the TDRA process](https://www.broadnet.me/answers/sender-id-registration-uae-tdra)
- [What is sender ID spoofing?](https://www.broadnet.me/answers/what-is-sender-id-spoofing)
- [What is A2P SMS?](https://www.broadnet.me/answers/what-is-a2p-sms)
- [A2P SMS](https://www.broadnet.me/products/a2p-sms)
- [SMS Firewall (operators)](https://www.broadnet.me/operators/sms-firewall)