Google Chrome is a freeware web browser developed by Google. It used the WebKit layout engine until version 27 and, with the exception of its iOS releases, from version 28 and beyond uses the WebKit fork Blink. It was first released as a beta version for Microsoft Windows on September 2, 2008, and as a stable public release on December 11, 2008. As of January 2015, StatCounter estimates that Google Chrome has a 51% worldwide usage share of web browsers, indicating that it is the most widely used web browser in the world. Google releases the majority of Chrome’s source code as an open-source project Chromium. A notable component that is not open source is the built-in Adobe Flash Player.