Definition
An alphanumeric sender ID is a text sender name such as “AcmeBank” shown instead of a phone number on an SMS. It can contain up to 11 characters and cannot receive replies.
Alphanumeric sender IDs are limited to 11 characters because the originating address field in the SMS transport layer (3GPP TS 23.040) carries them as GSM 7-bit packed text in up to 10 octets. Letters, digits and a small set of symbols are commonly accepted; spaces and special characters are handled inconsistently across operators.
They improve recognition and trust because the recipient sees the brand rather than an unknown number. That is why banks, airlines and government services use them for OTPs and alerts.
Because the ID is not a dialable number, recipients cannot reply. For conversations, opt-out by reply or surveys, use a short code or long code instead.
Many countries, including most GCC markets, require alphanumeric IDs to be registered with operators or the regulator before use, and may apply separate rules to promotional messages. Some countries do not support alphanumeric IDs at all and overwrite them with a numeric sender.
Avoid IDs that imitate other brands or generic words like “INFO” or “BANK”; operators often reject them as a fraud risk.
Example
ACME-Store (10 characters) — valid length; AcmeOnlineStore (15 characters) — too long, would be truncated or rejected.