Darwin is a version of the BSD UNIX operating system that offers advanced networking, services such as the Apache web server, and support for both Macintosh and UNIX file systems. Darwin is the core of Mac OS X. The Darwin kernel is based on FreeBSD and Mach 3.0 technologies and provides protected memory and pre-emptive multitasking. Darwin runs on PowerPC-based Macintosh computers and a version is also available for x86-compatible computers.

Darwin currently includes the Apache web server, sendmail, and some other services. By default, there is only one account (root) with no password, as with most UNIX systems. You can create additional accounts using standard UNIX tools.