In a move that amplifies competitive tensions with Microsoft and calls into question Google's longstanding relationship with Mozilla Corporation, Google on Monday announced a new open source browser called Google Chrome.

"Because we spend so much time online, we began seriously thinking about what kind of browser could exist if we started from scratch and built on the best elements out there," said Sundar Pichai, VP of product management at Google and Linus Upson, engineering director at Google, in a blog post. "We realized that the Web had evolved from mainly simple text pages to rich, interactive applications and that we needed to completely rethink the browser. What we really needed was not just a browser, but also a modern platform for Web pages and applications, and that's what we set out to build."

Google Chrome, built using elements of Apple's WebKit browser engine and Mozilla Firefox, will soon be available for Windows users. At the moment, Chrome exists only as an online comic. Versions for Mac OS X and Linux are planned.

Google Chrome includes a new JavaScript engine, called V8, to enhance Web application performance. It has been designed to handle multiple processes, each with its own memory and copy of global data structures. And each processes runs in its own sandbox, making it possible to have multiple Web applications open in different browser tabs without cross-application security risks.

Stung by its ongoing loss of browser market share to Mozilla's Firefox, Microsoft recently released Windows Internet Explorer 8 Beta 2. According to Net Applications, Microsoft Internet Explorer has 72.15% market share worldwide, down from 79% a year ago.

In response to Google's entry into the browser battle, Dean Hachamovitch, general manager of the Internet Explorer group, told The New York Times that Internet Explorer 8 is competitive with other browsers and will win over users by offering them more control over their personal data.

Mozilla CEO John Lilly said in his blog post that competition from Google would encourage Mozilla to improve Firefox and that he expects his company's collaborative and financial relationship with Google to continue. He said that Mozilla had just renewed its deal with Google to make Google the default search engine in Firefox through November 2011.

Google Chrome isn't only a challenge to Internet Explorer or Firefox; in conjunction with Google Gears, Chrome represents an attempt to provide an alternative to the desktop, specifically Microsoft Windows, as the IT world shifts toward a cloud computing paradigm.

Google has a lot of work to do before it can truly offer a cloud-based alternative to Windows, but with the arrival of Chrome, a major piece of the foundation has been laid.