Apple has announced the official release date of macOS Sierra 10.12 will be Tuesday, September 20. All users with a Mac compatible with macOS Sierra will be able to download and install the update free of charge from the Mac App Store.
macOS Sierra includes many new enhancements and features. Some of which includes Siri on the Mac, the ability to unlock a Mac using an Apple Watch, Safari with Apple Pay support, and a revamped Photos app with intelligent search, facial recognition, and a new Memories feature, as well as a Picture in Picture mode for watching floating video over other apps. Other useful utilities include an iOS to macOS clipboard, and an enhanced iCloud Drive features which can help offload data to iCloud when storage is running low.
According to Apple, the official compatible hardware list of Macs capable of running Mac OS Sierra 10.12 is as follows:
MacBook Pro (2010 and later)
MacBook Air (2010 and later)
Mac Mini (2010 and later)
Mac Pro (2010 and later)
MacBook (Late 2009 and later)
iMac (Late 2009 and later)