Man-Machine Interface codes, often abbreviated as MMI codes, are a series of short codes, typically beginning with or # symbols, that are entered on a mobile phone’s dialer to execute specific actions or access hidden menus. For example, a code might be used to check a device’s IMEI number (#06#) or to forward calls to another number.
These codes offer a quick and direct method to access configuration settings, troubleshoot issues, and retrieve device information without navigating through the phone’s settings menus. Their historical significance lies in their early adoption by mobile network operators for internal testing and diagnostics, which later extended to user-accessible functions.