Implementations

Mach has been forked many times. This table lists the ones most people ask about.

Name	Origin	Notes
CMU Mach	Carnegie Mellon, 1985 to 1994	The original. Mach 2.5 keeps BSD in the kernel, and Mach 3.0 is the microkernel. No longer developed.
Mach 4	University of Utah, 1994 to 1996	Built on CMU's Mach 3.0 code to fix its main problems. The GNU project moved to it for the Hurd.
GNU Mach	GNU project, from 1996	Descends from Mach 4. It is still the default microkernel of the GNU Hurd.
XNU	NeXT and Apple, 1990s to now	The kernel of macOS, iOS and the other Apple platforms. A modified Mach combined with BSD code and the IOKit driver framework in one kernel.
OSF/1	Open Software Foundation, from 1988	Started from Mach 2.5 and later versions used Mach 3.0. Digital's version became Digital UNIX, then Tru64 UNIX. Discontinued.
MkLinux	Apple and OSF Research Institute, 1996	Linux running as one server on Mach 3.0, for Power Macintosh. A demonstration of an OS personality in user space. Discontinued.
Mach X	New code, 2026	The kernel of KyberOS. A pure Mach microkernel for x86_64 with no BSD code in the kernel. Early development, runs in QEMU. This site is written by its authors.