Apple on Tuesday quietly announced it will release High Sierra, this year's upgrade of the Mac's operating system software, on Monday, Sept. 25.
As has been Apple's habit for several years, the date was posted on the company's website. The news did not rate a mention during the lengthy introductions of the year's new iPhones, the 8 and 8 Plus and the $999 iPhone X.
High Sierra will be the second under the "macOS" brand introduced in 2016, when Apple dropped the older "OS X" and formatted the Mac operating system label to match others in its stable, including iOS and tvOS. High Sierra is also known as macOS 10.13 using the Cupertino, Calif. company's numerical labeling.
The High Sierra release date is five days later on the calendar than last year's Sierra, and the third straight annual upgrade delivered in September.
According to High Sierra's system requirements, the OS will run on all Macs now running its predecessor: MacBooks and iMacs from late 2009 on; MacBook Pros, Mac Minis and Mac Pros from mid-2010; and MacBook Airs from late 2010 forward. Sierra, the 2016 upgrade, dropped support for older machines Apple made and sold in 2007 and 2008.
macOS High Sierra will be a free upgrade available from the Mac App Store.