Why is Xcode 12.2 as large as macOS Big Sur?

Just as the title says...

• Xcode 12.2 is a 11.4 GB
• MacOS Big Sur is a 12.18 GB

Xcode is just an application while Big Sur is a complete Operating System. How come a macOS application is as large as the OS itself?

Is Xcode bringing in components that are not part of the standard OS?

Solution 1:

Xcode 12.2 unpacked is 16.8 GB, 13.2 GB of which are platform operating systems.

• iPhoneOS.platform is 5.9 GB
• AppleTVOS.platform is 3.6 GB
• WatchOS.platform is 3.3 GB

In comparison, MacOSX.platform is only ~300 MB since most of the platform is already available in a normal installation of macOS. Xcode doesn't just build apps for macOS — it also builds apps for other operating systems and runs a simulator of each OS.

Solution 2:

Xcode is considerably more than just one application. Nowadays, it essentially bundles all developer tools, and all header files — practically everything that is only relevant to developers and not to end users.

You might find it instructive to open a terminal window and run

ls -lR /Applications/Xcode.app

or

du -m /Applications/Xcode.app