What is an SMS sender ID?
The sender ID is what appears in the “from” field of an SMS — a phone number, short code, or alphanumeric brand name. Rules for it differ per country, and spoofing it is a top phishing vector.
Definition
The sender ID is the originator field of an SMS — what the recipient sees as “from”. It takes three forms: a regular phone number (long code), a short code (5–6 digits leased for high-volume messaging), or an alphanumeric sender ID — up to 11 characters of brand name like “ACME” with no reply path. Which forms are allowed, and whether they must be pre-registered, varies sharply by country: alphanumeric IDs are standard across Europe, require registry filing in much of Asia and the Middle East, and are simply not delivered in the US, where 10DLC and short codes rule.
Sender ID is also a security surface. Because SMS has no built-in sender authentication, an unregistered alphanumeric ID can be spoofed on permissive routes — the mechanism behind most bank-impersonation smishing. Registries and carrier firewalls increasingly pin brand IDs to approved senders, and analytics platforms track which sender IDs appear on which routes to spot impersonation early.
Why it matters
The sender ID is your brand’s face in the inbox and a delivery variable at once: an unregistered ID silently rewritten to a random number destroys trust and response rates, while an unprotected one invites spoofing. Per- country sender ID strategy is a checklist item for any international rollout.
See it in action
Per-country sender ID handling in the SMPP gateway →