How to Decode Apple Version and Build Numbers

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You undoubtedly know about Apple’s version numbering scheme for its operating systems—iOS 13.5.1 and macOS 10.15.5, for instance. But did you know Apple also has a hidden build numbering scheme that can be even more useful? Former Apple engineer David Shayer explains how to decode build numbers and learn from them.

One interesting fact that’s worth mentioning:

On macOS, the major build number matches the Darwin kernel major version. See Wikipedia. With the exception of Mac OS X 10.0 (kernel 1.3.1), and 10.1 (kernel 1.4.1, later renumbered to 5), the two increment in lock-step with each other.

Surprisingly, Apple apparently chose to not do this for iOS/watchOS/tvOS.

I wonder if they will start sync’ing with each other in the future after ARM-based Macs ship, since all devices will (most likely) be running different builds of the same kernel.


Looks like Big Sur will identify itself as both 10.16 and 11.0, depending on the version of the SDK used.

Sounds like a reasonably good solution to a no-win situation.