macOS Sierra, iOS 10 public betas released

Today, Apple release the public betas of macOS Sierra and iOS 10. You need to enroll your device through the Apple Beta Software Program; you can always go back to the released versions, or keep using the betas until they update to the final versions once the time has come. As always, install them at your own peril - and for the love of Fiona, don't do it on devices you rely on.