High Quality Content by WIKIPEDIA articles! The Unified Extensible Firmware Interface (UEFI) is a specification that defines a software interface between an operating system and platform firmware. UEFI is meant as a replacement for the Basic Input/Output System (BIOS) firmware interface, present in all IBM PC-compatible personal computers. In practice, most UEFI images have legacy support for BIOS services. It can be used to allow remote diagnostics and repair of computers, even without another operating system.