Safari Technology Preview is Apple’s experimental Safari where features are tested before being officially released for the browser. Currently, the software is being based on the macOS Big Sur Safari 14 update, which includes web extension support, touch ID web authentication, password breach notifications, tab previews and more.
The new update is available for macOS Big Sur and macOS Catalina and can be downloaded via the Software Update in System Preferences. Release notes can be found on the official Safari Technology Preview page.
Apple intends to collect developer feedback and users during the browser’s experimental phase. The software can run with official Safari releases and does not require a developer account.