Apple released third beta releases iOS 11, macOS High Sierra and tvOS 11 to beta users.
Currently iOS 11 beta 3, macOS High Sierra 10.13 beta 3, and tvOS beta 3 are available for installation by members of the developer beta program. Beta 3 for public testing has not yet been released – usually the release of these firmwares is carried out shortly after the release of test versions for developers.
iOS 11 beta 3 can be downloaded via Software Update in the standard 'Settings' application.
macOS 10.13 High Sierra beta 3 is available for download in the Mac Updates tab App Store.
You can install tvOS 11 beta 3 through the settings menu Apple TV.
The watchOS 4 beta update is also expected to be released soon for beta participants Apple Watch.
Beta software is less stable compared to final public releases, so it is most suitable for advanced users, although public beta testing programs are readily available to anyone. The public beta iOS 11 can be installed (and rolled back if necessary), just like in the case of macOS High Sierra (then a rollback is possible if there is a backup in Time Machine).
The final versions of operating systems iOS 11 and macOS High Sierra will be released this fall.
How to download iOS 11 Beta 1 and macOS 10.13 Beta 1
Download iOS 11 Beta 2, macOS High Sierra Beta 2 for Developers
iOS 10.3.3. and macOS 10.12.6 beta 6 are available for testing