Fulfilling a promise it made at WWDC in June, Apple has released the first public betas of iOS 10 and macOS Sierra on Thursday, giving an early glimpse at software that won't be finished until sometime this fall. [Updated]
Access to the both downloads is restricted to members of the Apple Beta Software Program. Unlike Apple's developer program, however, the Beta Software Program is free, and should offer more stable code than some developer seeds.
Users should nevertheless be cautious about installing beta code on a primary device, since it can still potentially cause issues like crashes, battery drain, or slow performance.