Apple this week unveiled what it is calling Safari Technology Preview, which is a middle ground between public releases of the web browser and Webkit Nightly builds for developers.
Apple describes the preview browser by saying :
Safari Technology Preview gives you an early look at upcoming web technologies in OS X and iOS including the latest layout technologies, visual effects, and developer tools so you can provide input on how they are implemented and deliver a best-in-class user experience on all Apple devices.
Safari Technology Preview gives web developers a preview of improvements to Safari’s rendering engine, WebKit, along with developer tools like Responsive Design Mode built directly into Safari. The Technology Preview features the latest version of WebKit, along with a bug reporter to report issues.
The largest advantage compared to Webkit nightlies is Safari Technology Preview updates from the Mac App Store “every few weeks” according to Apple. It also runs side by side with the release version of Safari, for comparisons and testing new features without breaking your current code.
The Safari Technology Preview is available from the Apple Developer website now, for free.