The Multiboot Specification is an open standard describing how a boot loader can load an x86 operating system kernel. The specification allows any compliant boot loader implementation to boot any compliant operating system kernel. Thus, it allows different operating systems and boot loaders to work together and interoperate, without the need for operating system–specific boot loaders. As a result, it also allows easier coexistence of different operating systems on a single computer, which is also known as multi-booting.
The specification was originally created in 1995 and developed by the Free Software Foundation. GNU Hurd, VMware ESXi, Xen, and L4 microkernels all need to be booted using this method. GNU GRUB is the reference implementation used in the GNU operating system and other operating systems. As of January 2015, the latest version of Multiboot Specification is 0.6.96, defined in 2009.
Software known to be compliant with the Multiboot Specification includes AROS Research Operating System, OpenBIOS, CapROS, freeldr (bootloader of ReactOS), GNU Hurd, GRUB 2, Linux, MirBSD bootloader, MINIX 3, NetBSD, illumos, SkyOS, Syllable, and Xen.