https://techcrunch.com/2017/09/25/macos-high-sierra-is-available-now-as-a-free-download/

The latest version of of macOS just went live on the Mac App Store as a free download. Apple’s other operating system has taken a bit of a backseat to its mobile counterpart in recent years, and High Sierra’s no exception. That’s due in part to the bonanza features in iOS 11 and the fact that macOS 10.13 is a pretty unsexy update, mostly focused on infrastructural changes.

It’s an important one, though. The big change here is the first meaningful update to Apple’s file system in around 30 years. Crazy to think, but all of the OS X updates used the same system the company has relied on since the early days of the Mac. That update will be mostly invisible to users in the short term, but it will help futureproof the operating system for years to come.