According to JavaScript rendering tests run by Computerworld, the public beta of Safari 4 is in a virtual dead heat with the most recent edition of Google's Chrome, but is 38% faster than the newest version of Firefox, more than three times faster than the production edition of that open-source browser, and over five times faster than Microsoft's Internet Explorer 8.

Computerworld ran the SunSpider JavaScript benchmark suite in Windows XP three times for each browser, then averaged the scores.

Safari 4, which Apple , scored just slightly higher than Chrome 2.0.164.0, a developer-only build of Google's browser that was issued only last week. The difference, however, was minute: Google was only about 7% faster. Although Chrome and Safari are both built around the same open-source WebKit engine, they use different JavaScript engines. The former features Google's own V8 engine, while Safari 4 relies on Apple's new Nitro.

That new engine was most in evidence when Safari 4's scores are compared to those of Safari 3.2.2, the current shipping version on Windows: The beta of Safari 4 was about 3.7 times faster.

Safari 4 also proved faster than the newest Firefox, a nightly build in the run-up to Firefox 3.1, although at just 38% faster its edge was much smaller.