After seeding iOS 9.3.3 beta 2 and OS X El Capitan 10.11.6 beta 2 to the registered members of the Apple Developer Program yesterday, these new betas are now available to public beta testers who are signed on the Apple Beta Software Program.
Public beta testers can apply these updates through the Software Update mechanism on devices enrolled into the Beta program that run a prior iOS/OS X beta.
These new betas don’t provide any new user-facing features as Apple is getting ready to preview the next major versions of its software platforms at WWDC next week.
iOS 9.3.3 beta 2 comes with a build number of “13G21” while OS X El Capitan 10.11.6 beta 2 has a build number “15G12a”. In addition, Apple yesterday also seeded tvOS 9.2.2 beta 2 (build “13Y816”) and watchOS 2.2.2 beta (build “13V601”).
watchOS and tvOS betas are not currently available for public beta testing.