
Apple on Monday announced macOS High Sierra, the next major version of its operating system for Mac computers.

macOS High Sierra is compatible with any Mac capable of running macOS Sierra, as Apple has not dropped support for any older models this year.
The official list of Mac models compatible with macOS High Sierra:
Late 2009 or Later
MacBook
iMac / iMac Pro
2010 or Later
MacBook Air
MacBook Pro
Mac mini
Mac Pro
To determine your Mac's model year, click on the Apple logo in the top-left menu bar and select About This Mac.
The first macOS High Sierra beta was released to registered Apple developers on Monday. A public beta will be available in late June through the Apple Beta Software Program. The software update will be officially released in the fall.
Article Link: Macs Able to Run macOS Sierra Remain Compatible With High Sierra