On Monday afternoon, Apple released an update to just one of its eight currently running OS betas, and unveiled the fourth beta of macOS Sierra 10.12.6

The Mac update can be downloaded through Apple's developer portal, or through the software update feature on properly registered devices. 

The current build is 16G18a. The previous build from June 13 was 16G16b. There are no particular avenues of testing listed by Apple in the release notes for the update.

Also running are the first betas for iOS 11, macOS 10.13 High Sierra, watchOS 4 and tvOS 11, rolled out shortly after introduction during WWDC. Apple's iOS 11 appears to carry the most changes, with upgrades to Siri, Apple Pay, Photos and a general user interface revamp.

The macOS High Sierra update contains a number of refinements and other improvements like Apple File System integration, migration from H.264 to H.265, and Metal 2.

Source: appleinsider