Safari Technology Preview release 70 contains bug fixes and enhancements for web animations, cross-browser, CSS, WebRTC, Rendering, Web Inspector, Storage, Media, Payment Request, and Security UI.
The new version of Safari Technology Preview is available for MacOS High Sierra and MacOS Mojave, the latest version of the Mac OS that was released to the public in September.
Updating Safari Technology Preview is available through the Mac App Store software update mechanism for anyone who 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 be run side by side with the existing Safari browser, and when developed for developers, it does not require a developer account to download.