Apple has released the third public betas of macOS 10.13 High Sierra, iOS 11 and tvOS 11. The finished versions are due this fall.
The public betas are available on Apple's Beta Software Program website. Just remember that beta software, so proceed with care.
Apple does public betas in order to increase the size of the pool of testers. The tech giant recommends keeping back-ups of your files before installing a public beta.