The Unstructured Supplementary Service Data (USSD) is a Global System for Mobile (GSM) protocol that has been around since 1997.
It allows users to enter a combination of numbers, asterisks, and hashes in their regular dialling app to execute various actions on their mobile network account.
Although GSM, which includes 2G and 3G technologies, is set to be shut down over the next few years, USSD can be supported on LTE and 5G.
If you know the shortcodes your mobile operator uses for the various services, then USSD is often the fastest option for managing your cellular plan.
It also does not require an Internet connection or consume mobile data. When you’ve run out of airtime or data, the right USSD code can be a lifesaver.
Some are really useful, like being able to send a “please call me back” message, or sending airtime to another user, or requesting airtime from another user.