After introducing major versions of all four of its software platforms, Apple is now letting registered developers to go to their developers accounts and download the betas on their devices. So if you are developer or a curious power user who wants to try out the new iOS 10 beta, macOS 10.12 Sierra beta, tvOS 10 beta and watchOS 3 beta on your devices, then now is your chance to do so. Please be warned since its the first beta, the softwares are going to have many bugs. It is a good idea to not install the beta updates on your daily drivers.
For iOS 10 Apple is allowing developers to either download the whole iOS IPSW file on their computer and restore through iTunes, or download a configuration profile that would allow them to update over-the air. A similar option is available to tvOS 10 users. If you own an Apple Watch and want to try watchOS 3 on it then you have to download the configuration profile on your iPhone and install it before you can proceed to download the watchOS beta. For macOS 10.12, you can download a 5GB file and install the beta right away.
In addition to software updates, Xcode 8 beta has also been uploaded by Apple and is available for download through the dev center.