Safari is a web browser developed by Apple Inc. and included with the Mac OS X and iOS operating systems. First released as a public beta on January 7, 2003 on the company's Mac OS X operating system, it became Apple's default browser beginning with Mac OS X v10.3 "Panther". Safari is also the native browser for iOS. A version of Safari for the Microsoft Windows operating system, first released on June 11, 2007, supports Windows XP, Windows Vista, and Windows 7. The latest stable release of the browser is 5.1.1, which is available as a free download for both Mac OS X and Microsoft Windows. As of 2011, Safari is the fourth most widely used browser in the US, following Internet Explorer, Mozilla Firefox, and Google Chrome.