Apple has released a version of Safari for OS X called Safari Technology Preview. The app contains bleeding edge browser features that is under development, and is meant for web developers to help them get ready.
Safari Technology Preview is a version of Safari for OS X, distributed by Apple, that includes a cutting-edge, in-development version of the WebKit browser engine. It’s a great way to test upcoming WebKit features and give feedback to the people building them when it’s most useful — early on in development.
Web engine technology is evolving at a fast pace, both Chrome and Firefox have had a preview version of their browsers for years. Apple has finally made an effort to be helpful to web developers. Safari Technology Preview is useful for developers targeting iOS as the same WebKit engine is used in both OS X and iOS.
Download is free without registration for anyone at Apple developer website. You can run the preview app side-by-side with Safari and other browsers. Updates to the app will be delivered via Mac App Store.