A key feature -- if not the key feature -- in Safari 4 beta, is the SquirrelFish/Nitro JavaScript interpreter. WebKit calls its boosted JavaScript SquirrelFish, not exactly glossy brochure material. Apple renamed it Nitro Engine. JavaScript is the "j" in "AJAX," so is responsible for first page draw latency. To do the fastest browser takes the fastest JavaScript, but also quick server communication.

Apple's "fastest browser" boast is proved by SunSpider JavaScript Benchmark tests against Firefox 3.0.5, both running on OS X Leopard 10.5.6. The is freely available online, where you can test any browser you like. Note that the benchmark resides on WebKit's site. Mozilla and Microsoft should challenge the results if they feel their browsers are misrepresented.

In my runs of the SunSpider benchmark, Safari 4 beta skunked Firefox, which is the primary browser for POSIX platforms. (See the for my results.) With Apple's backing and a quick chain for distributing updates, Safari is a browser you need to have. You can download Safari 4 beta, and browse features and screen images, at .

Other features make Safari 4 flat irresistible. It's the first desktop release to support the local database features of HTML 5. The information and Web apps traditionally only available when you're linked to the network can be accessed locally. WebKit, nee Safari 4 beta, has a facility for examining and structuring tables and fields.

Field fill-in for URLs and keyword searches are attempted with each keystroke, for both the URL and search fields. The most likely matches show in a drop-down list populated by Google. URL matches are taken from Safari's history. The sites you visit most often can be displayed as a matrix of thumbnails when Safari 4 launches, and pages in your history can be leafed through in Cover Flow. When the RSS for a page is updated, an indicator lights up for that thumbnail.