The macOS SDK (formerly "OS X SDK") provides all the types and classes made available by Apple for creating applications and other projects for the Mac.

Each Cocoa SDK is spread over several frameworks and core include files. The core C APIs are located in rtl.fx, which is a package containing pretty much everything defined in /usr/include. The base framework of core Cocoa classes is called "Foundation" (shared with macOS), and contains, among many other things, NSObject, the base type for all Cocoa classes.

More frameworks are shared across sub-platforms, while each sub-platform also provides its own unique frameworks.

Please refer to the Introduction to the Frameworks topic for more information on how the frameworks fit together, and how they differ between the (currently) four separate Cocoa platforms.

For all the SDK frameworks, the Namespace used matches the framework name.

macOS is the oldest of the four platforms, and the ancestor of iOS (and iOS's watchOS and tvOS siblings). As such, it shares many of the lower-level non-UI frameworks with those platforms, but provides its own paradigms for GUI development, in AppKit and related frameworks.

In addition to the macOS SDK, you can also build applications for the Mac using the [iOS]((iOS) SDK, with Mac Catatyst.

See Also

macOSiOStvOSvisionOSwatchOSMac Catatyst