Unified Extensible Firmware Interface

The Unified Extensible Firmware Interface (UEFI) is a specification that defines a software interface between an operating system and platform firmware. UEFI replaces the Basic Input/Output System (BIOS) firmware interface originally present in all IBM PC-compatible personal computers, with most UEFI firmware implementations providing legacy support for BIOS services. UEFI can support remote diagnostics and repair of computers, even with no operating system installed.

Intel developed the original Extensible Firmware Interface (EFI) specification. Some of the EFI's practices and data formats mirror those from Microsoft Windows. In 2005, UEFI deprecated EFI 1.10 (the final release of EFI). The Unified EFI Forum is the industry body that manages the UEFI specification.

The original motivation for EFI came during early development of the first Intel–HP Itanium systems in the mid-1990s. BIOS limitations (such as 16-bit processor mode, 1 MB addressable space and PC AT hardware) had become too restrictive for the larger server platforms Itanium was targeting. The effort to address these concerns began in 1998 and was initially called Intel Boot Initiative. It was later renamed to Extensible Firmware Interface (EFI).

In July 2005, Intel ceased its development of the EFI specification at version 1.10, and contributed it to the Unified EFI Forum, which has evolved the specification as the Unified Extensible Firmware Interface (UEFI). The original EFI specification remains owned by Intel, which exclusively provides licenses for EFI-based products, but the UEFI specification is owned by the Forum.

Version 2.1 of the UEFI specification was released on 7 January 2007. It added cryptography, network authentication and the User Interface Architecture (Human Interface Infrastructure in UEFI). The latest UEFI specification, version 2.6, was approved in January 2016.

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