What is USSD (Unstructured Supplementary Service Data)
USSD is a communication method for GSM mobile phones that occurs in real-time as opposed to texting via SMS where the recipient can receive your text minutes, hours or even days later.
USSD codes are used by a mobile phone network to deliver text information to a mobile phone. You enter a USSD code into your phone as if you were dialling a number, then you press send and the network sends back a text reply if the code is recognised and supported.
USSD codes start with an asterisk (*) and end in a hash (#) and contain numbers or further asterisk and hash characters in-between. USSD codes are free to send.
Most USSD codes are sent to a USSD computer on the network to process but some are designed to be processed by the phone itself, such as *#06# for displaying your phones IEMI number. Some are designed to be interpreted by the SIM card in the phone, such as change PIN.
USSD codes can be initiated by you the user, such as when requesting your balance (on PAYG), or can be initiated by the network such as telling you how much credit you have remaining after making a call or sending a text.
On old handsets USSD messages look just like a text message. On new phones, especially smart phones they appear in a pop-up window in formatted text.
USSD codes can be saved in your phone / SIM memory as a stored number. Some networks provide these codes pre-saved under aliases such as "Check balance" and "Customer services". If you buy your handset from a network provider then the more popular USSD codes will be added as hot-keys. For instance holding down "3" on your keypad may activate the USSD code to check your balance.
This article would be far too long if I tried to list the supported USSD codes for each mobile phone operator in the world, therefore if you are interested in knowing the USSD codes that your network provider supports I recommend typing "USSD operator" into Google, replacing "operator" with your network provider's name. For example "USSD Orange".
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Article date: 19th May 2013