The new version of Safari Technology Preview is available for both macOS High Sierra and macOS Mojave, the latest version of the Mac operating system released to the public in September 201
Updating Safari Technology Preview is available through the software update mechanism in the Mac App Store to anyone who has downloaded the browser. Full release notes for the update are available on the Safari Technology Preview site.
Apple's goal with Safari Technology Preview is to gather feedback from developers and users on the browser's development process. Safari preview can run side by side with the existing Safari browser, and when developed for developers, it does not require a developer account to download.