Darwin (operating system)

Darwin
Developer	Apple Inc.
Written in	C, C++, Objective-C, assembly language
OS family	Unix-like, FreeBSD, BSD
Working state	Current
Source model	currently open source with proprietary components[citation needed], previously open source
Initial release	November 15, 2000; 24 years ago
Latest release	24.0.0 / September 16, 2024; 2 months ago
Repository	github.com/apple-oss-distributions/distribution-macOS
Platforms	Current: x86-64, 64-bit ARM, 32-bit ARM (32-bit ARM support is closed-source); Historical: PowerPC (32-bit and 64-bit), IA-32
Kernel type	Hybrid (XNU)
Influenced by	NeXTSTEP, FreeBSD, BSD
Default; user interface	Command-line interface (Unix shell)
License	Mostly Apple Public Source License (APSL), with closed-source drivers
Official website	opensource.apple.com

Darwin is the core Unix-like operating system of macOS, iOS, watchOS, tvOS, iPadOS, audioOS, visionOS, and bridgeOS. It previously existed as an independent open-source operating system, first released by Apple Inc. in 2000. It is composed of code derived from NeXTSTEP, FreeBSD,^[3] other BSD operating systems,^[6] Mach, and other free software projects' code, as well as code developed by Apple. Darwin's official mascot is Hexley the Platypus. ^[7]

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Darwin is mostly POSIX-compatible, but has never, by itself, been certified as compatible with any version of POSIX. Starting with Leopard, macOS has been certified as compatible with the Single UNIX Specification version 3 (SUSv3).^[8]^[9]^[10]

The heritage of Darwin began with Unix derivatives supplemented by aspects of NeXT's NeXTSTEP operating system (later, since version 4.0, known as OPENSTEP), first released in 1989. After Apple bought NeXT in 1996, it announced it would base its next operating system on OPENSTEP. This was developed into Rhapsody in 1997, Mac OS X Server 1.0 in 1999, Mac OS X Public Beta in 2000, and Mac OS X 10.0 in 2001.

In 1999, Apple announced it would release the source code for the Mach 2.5 microkernel, BSD Unix 4.4 OS, and the Apache Web server components of Mac OS X Server.^[11] At the time, interim CEO Steve Jobs alluded to British naturalist Charles Darwin by announcing "because it's about evolution".^[12] In 2000, the core operating system components of Mac OS X were released as open-source software under the Apple Public Source License (APSL) as Darwin; the higher-level components, such as the Cocoa and Carbon frameworks, remained closed-source.

Up to Darwin 8.0.1, released in April 2005, Apple released a binary installer (as an ISO image) after each major Mac OS X release that allowed one to install Darwin on PowerPC and Intel x86 systems as a standalone operating system.^[13] Minor updates were released as packages that were installed separately. Darwin is now only available as source code. As of January 2023, Apple no longer mentions Darwin by name on its Open Source website and only publishes an incomplete collection of open-source projects relating to macOS and iOS.

Kernel

The kernel of Darwin is XNU, a hybrid kernel which uses OSFMK 7.3^[14] (Open Software Foundation Mach Kernel) from the OSF, various elements of FreeBSD (including the process model, network stack, and virtual file system),^[15] and an object-oriented device driver API called I/O Kit.^[16] The hybrid kernel design provides the flexibility of a microkernel^[17]^{[failed verification – see discussion]} and the performance of a monolithic kernel.^[18]

Hardware and software support

The last bootable full release of Darwin supported 32-bit and 64-bit Apple PowerPC systems and 32-bit Intel PCs.^[19]

Darwin currently includes support for the 64-bit x86-64 variant of the Intel x86 processors used in Intel-based Macs and the 64-bit ARM processors used in the iPhone 5S and later, the 6th generation iPod Touch, the 5th generation iPad and later, the iPad Air family, the iPad Mini 2 and later, the iPad Pro family, the fourth generation and later Apple TVs, the HomePod family, and Macs with Apple silicon such as the 2020 Apple M1 Macs, as well as the Raspberry Pi 3B.^[20]^[21] An open-source port of the XNU kernel exists that supports Darwin on Intel and AMD x86 platforms not officially supported by Apple, though it does not appear to have been updated since 2009.^[22] An open-source port of the XNU kernel also exists for ARM platforms, though it has not been updated since 2016.^[23] Older versions supported some or all of 32-bit PowerPC, 64-bit PowerPC, 32-bit x86, and 32-bit ARM.

It supports the POSIX API by way of its BSD lineage (largely FreeBSD userland), so a large number of programs written for various other UNIX-like systems can be compiled on Darwin with no changes to the source code.

Darwin does not include many of the defining elements of macOS, such as the Carbon and Cocoa APIs or the Quartz Compositor and Aqua user interface, and thus cannot run Mac applications. It does, however, support a number of lesser-known features of macOS, such as mDNSResponder, which is the multicast DNS responder and a core component of the Bonjour networking technology, and launchd, an advanced service management framework.

In July 2003, Apple released Darwin under version 2.0 of the Apple Public Source License (APSL), which the Free Software Foundation (FSF) classifies as a free software license incompatible with the GNU General Public License.^[24] Previous versions were released under an earlier version of the APSL license, which did not meet the FSF definition of free software, although it did meet the requirements of the Open Source Definition.^[25]

The following is a table of major Darwin releases with their dates of release and their derivative operating system releases.^[26] Note that the corresponding releases may have been released on a different date.