Safari Technology Preview, a new version of its Safari web browser, is designed specifically for developers and is Apple's foray into the area of web development
It offers developers a sneak peek into what the Safari of the future would look and work like – including the latest visual effects and layout technologies - while giving them the opportunity to influence the direction it takes via feedback.
What you can do with Safari Technology Preview:
Give it a try: You can experiment with these technologies by downloading Safari Technology Preview (OS X 10.11.4 or later) from Apple’s developer pages. Updates occur every few weeks and include the most recent additions and improvements to WebKit (the rendering engine that powers Safari).