Built for speed
The big behind-the-scenes news is the introduction of the , a super-fast JavaScript engine that executes JavaScript up to 30 times faster than Internet Explorer 7, and three times faster than Firefox 3. To get a sense of the speed increase, I ran a quick test using the on our 2.66GHz iMac with 2GB of RAM. I ran SunSpider in Safari 3, Safari 4 Beta, and Firefox 3.0.6, to get a sense of the speed differences amongst the browsers.
The results were dramatic--Safari 4 completed the tests in 757ms, versus 2970ms for Safari 3 and 3028ms for Firefox 3.0.6. I also tested Firefox 3.1, currently in beta, which has its own advanced JavaScript engine. It was notably faster than Firefox 3.0.6, coming in at 1419ms, but still well behind Safari 4.
Outside of the JavaScript engine, Safari 4 seems to load pages very quickly, though page loading times on a fast network are quick enough that it's very hard to hand-time any differences in loading speed. Still, Safari 4 feels quite peppy on even the heaviest of sites. It also passes the , which checks how well a Web browser follows certain Web standards, with a perfect score.
Safari 4 also adds some bleeding-edge web technologies such as HTML 5's media support (making it easier to add audio and video to Web sites) and offline support (so developers can write web apps that run even without an internet connection); CSS effects (which enable animations, like , without a lot of complex code or Flash); and speculative loading (which loads the files required to view a web page before you need them).