List of Android Hidden Codes (USSD secret codes)

Android hidden codes are very useful when you want to access some information on your phone or want to do a testing and troubleshooting. But usually phone companies doesn't include these USSD secret codes to their manuals. To understand more about this, let us define USSD first. USSD code is the abbreviation of Unstructured Supplementary Service Data, sometimes referred to as "Quick Codes"