Safari 4.0 (Beta) is a web browser developed by Apple Inc, available for download in full install version for Windows platforms from legacy sources. This version of Safari was officially released on 2008-06-11 for public access and a brief summary of important updates and change log pertaining to this edition can be read below.

Safari 4.0 is the major release of the browser  with key change being the introduction of the fastest  JavaScript engine named SquirrelFish. According to the development team this interpreter can execute Java scripts four times faster than Firefox 3 and eight times faster than Internet Explorer 8.

Unlike its predeceasing versions this version of Safari has passed Acid3 test adhering to web standards compliance. There are many other changes including support for CSS Canvas, Speculative loading, and improved GUI.