The new macOS Big Sur was unexpectedly shown in Apple's keynote as being version 11.0, but the version developers are getting is still being called 10.16.
It's only a version number, but it's a significant one — and unusually confusing. Where there was much speculation over what Apple's new macOS would be named, there was none about the number. It was going to be macOS 10.16, until it wasn't. And then until it might be again.
Shown on screen during the WWDC 2020 keynote, macOS Big Sur was clearly identified as being macOS 11.0. While it wasn't remarked upon during the presentation, it was noticeable because it signifies Apple's first break from the numbering it has used since March 2001.
That was when what was then called Mac OS X was released as version 10.0, replacing the old Mac OS 9. It was a line drawn under the old, classic Mac as it had fundamentally been since the machine's first release in 1984. It was a line that marked the start of the new, modern OS X.
Fifteen versions of this followed, with Apple sticking to the version 10 number even as it passed version 10.9, Mavericks, in 2013. So Big Sur's move to version 11 is big, and perhaps fitting of such a major release which comes alongside the start of the move to Apple Silicon.
However, developers who have now received the first beta version of macOS Big Sur to test, report that it identifies itself as macOS 10.16.
There is speculation that version 11 represents the edition of macOS Big Sur that has been produced for the new Apple Silicon system. That would fit with how its number was shown on screen during Craig Federighi's presentation about Apple Silicon.
"I'm just going to open up 'About This Mac'," he said during the demonstration, "and what you see here is that we are running on our Apple Development Platform... Now, I have a confession to make. This isn't the first time you've seen Mac OS running here."
"In fact," he continued, "this is the same Mac that Beth [Dakin, Safari Software Engineer] and I used to demo all the new Big Sur features earlier."
State of the platform
Adding further fuel to the discussion fire, at the State of the Platform presentation after the keynote, Apple engineers explicitly referred to MacOS Big Sur as "macOS 11."