What is the USSD code * 123?

The USSD code *123, typically followed by a hash (#) as *123#, is commonly used by mobile network operators for quick access to various services. For example, it is widely used to check a mobile account balance or plan validity, as confirmed by providers like Airtel and BSNL in India. USSD (Unstructured Supplementary Service Data) codes allow communication between your phone and network, requiring no internet access. Its exact function can vary based on your mobile provider.