An SMS shortcode is a 5 digit number to which an SMS text message can be sent. Shortcodes are often used by businesses to allow customers to opt-in to their SMS campaigns, alert services, or to enter SMS competitions.
Short codes, or short numbers, are short digit sequences, significantly shorter than telephone numbers, that are used to address messages in the Multimedia Messaging System (MMS) and short message service (SMS) systems of mobile network operators. In addition to messaging, they may be used in abbreviated dialing.
Short codes are widely used for value-added services such as charity donations, mobile services, ordering ringtones, and television program voting. Messages sent to a short code can be billed at a higher rate than a standard SMS and may even subscribe a customer to a recurring monthly service that will be added to the customer's mobile phone bill until the user texts, for example, the word "STOP" to terminate the service.
Short codes are often associated with automated services. An automated program can handle the response and typically requires the sender to start the message with a command word or prefix. The service then responds to the command appropriately.