As it’s done with past releases, Apple today released the open source code of OS X 10.11 El Capitan. The release comes after Apple made good on its promise to open source its Swift programming language last week.

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Apple updated its Open Source webpage last night, where it also provides downloads to open source code for current and past releases of its developer tools, iOS, and OS X Server, with downloads of the OS X 10.11 source code for developers interested in taking a look.

Apple’s open source release of OS X (aka Darwin) has been around since 2000 and usually arrives in the weeks following the public release of OS X. 

Darwin is an open sourceUnix-like computer operating system released by Apple Inc. in 2000. It is composed of code developed by Apple, as well as code derived from NeXTSTEP,BSD, and other free software projects.

Darwin forms the core set of components upon which OS X and iOS are based. It is mostlyPOSIX compatible, but has never, by itself, been certified as being compatible with any version of POSIX. (OS X, since Leopard, has been certified as compatible with the Single UNIX Specification version 3 (SUSv3).

The open source code comes as the latest release of OS X, 10.11.2, hit the Mac App Store earlier today. Read more about Apple’s history of open sourcing here.

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