Earlier today, Apple released new developer betas for iOS 10, watchOS 3, and tvOS 10. At the time, macOS 10.12 Sierra beta 3 was notably missing; however, the company has now seeded the build.
The new build number is 16A254g. As usual, it comes alongside a long list of fixes and known issues.
The big new feature in macOS Sierra is Siri, a feature that iPhone users have had since iOS 5. While containing the features of its iOS counterpart, it also adds some that are specific to Macs, such as the ability to pin sports scores.
Other features include those that can be found in iOS 10, such as the ability for Photos to group your pictures by people, places, and things. You"ll also be able to unlock your Mac with your Apple Watch, but two-factor authentication needs to be set-up before this will work.
macOS 10.12 Sierra is also the first version of Apple"s PC operating system to end support for old Macs since OS X 10.8 Mountain Lion. Late 2009 iMacs and MacBooks are supported, as well as 2010 Macbook Airs, MacBook Pros, Mac Minis, and Mac Pros.