Software giant Microsoft Corp. wants to leave no stone unturned to challenge Google Inc. as it has announced Monday to release a free internet based version of its Office software to compete with Google's 3-year old well-established, free online Docs suite.

Microsoft's application will include lightweight versions of Word, Excel, PowerPoint and OneNote when it ships next year.

Last week Google announced it would launch a free operating system to compete with the software giant.

Microsoft's current move will enable 400 million customers to get to the Office web applications free of cost.

Now users can run Microsoft excel spreadsheets in the browser.

As per reports number of Office editions will also be trimmed down to 5 from 8. Microsoft further informed that users will be able to preview the new Office 2010 starting Monday.

Google is not the only competitor Microsoft is facing. Other web browsers such as Chrome, Mozilla Firefox have already took a large bite from Internet Explorer's market share.

However, according to the Wall Street Journal Microsoft's free online software can run off with as much as 4 billion U. S dollars in revenue.

Just after the announcement, Microsoft's shares soared to $23.23, up 3.8 percent.