Previewed at WWDC, launching in the fall.
Apple Launches Public Betas of iOS 9 and OS X El Capitan
iOS and Mac users interested in trying out the public betas can sign up on Apple's beta software program page.
We'll be looking for any changes specific to the public beta versions, but they are almost certainly essentially identical to the developer seeds released yesterday.
iOS 9 is the first major version of Apple's mobile operating system to see a public beta release, as the company did not initiate the program for iOS until iOS 8.3 earlier this year. OS X users may already be familiar with the public beta process, as a similar program was in place for OS X Yosemite last year.