Unstructured Supplementary Service Data
communications protocol
Unstructured Supplementary Service Data (USSD), sometimes referred to as "quick codes" or "feature codes", is a communications protocol used by GSM cellular telephones to communicate with the mobile network operator's computers. USSD can be used for WAP browsing, prepaid callback service, mobile-money services, location-based content services, menu-based information services, and as part of configuring the phone on the network. The service does not require a messaging app, and does not incur charges.
USSD messages are up to 182 alphanumeric characters long. Unlike short message service (SMS) messages, USSD messages create a real-time connection during a USSD session. The connection remains open, allowing a two-way exchange of a sequence of data. This makes USSD faster than services that use SMS.
While GSM is being phased out in the 2020s with 2G and 3G technologies, USSD services can be supported over LTE and 5G.
Uses
When a user sends a message to the phone company network, it is received by a computer dedicated to USSD. The computer's response is sent back to the phone, generally in a basic format that can easily be seen on the phone display. Messages sent over USSD are not defined by any standardization body, so each network operator can implement whatever is most suitable for its customers.
USSD can be used to provide independent calling services such as a callback service (to reduce phone charges while roaming), enhance mobile marketing capabilities or interactive data services.
USSD is commonly used by prepaid GSM cellular phones to query the available balance.
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This entry incorporates text from “Unstructured Supplementary Service Data” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.