Apple today released a new update for Safari Technology Preview, the experimental browser Apple first introduced on March 30, 2016. Apple designed the Safari Technology Preview to test features that may be introduced into the release version of Safari.
The Safari Technology Preview update 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 website.
Apple's goal with Safari Technology Preview is to gather feedback from developers and users on its browser development process. Safari Technology Preview can be run side-by-side with the existing Safari browser and while aimed at developers, it does not require a developer account to download.