Microsoft surprised a lot of people when they, out of nowhere, announced that Microsoft Office for iPad, iPhone, and Android is now free. The software company’s surprise may be a strategy to keep consumers using Word, Excel, and PowerPoint if a competing product is produced.

A few days ago, Microsoft announced a new partnership with Dropbox, an app that allows users to save photos to all their computers, tablets, and phones, no matter where they are or what device they are using. Users will now be able to use Office on Android and Apple products, storing all documents on Dropbox without having to pay anything.

The Verge  says that people may think Microsoft is crazy for making their Office suite free, but the company argues that it’s “a matter of moving its free web apps to mobile.” Michael Atalla, head of Office marketing, says that “It’s not a total strategic shift, as much of an extension of the existing strategy.” Currently, Microsoft Office apps are free online, and Atalla says that they’re taking the online user experience of Microsoft Office to iOS and Android, allowing consumers to be productive from any device.

Microsoft Office revenue won’t be a problem because the free Microsoft Office for iPad, iPhone, and Android doesn’t pertain to businesses. All businesses storing and editing their documents on OneDrive for Business or Dropbox for Business will still have to purchase an Office 365 subscription. There will also be premium upgrades that consumers can purchase, which will also help keep Microsoft revenue up.

Tom Warren claims that the threat of Office competition is the reason for Microsoft’s mobile shift. It would be easy for competitors to build a rival product and offer it for free. Now that Microsoft Office for iPad, iPhone, and Android is free, competitors will find it difficult to steal away Microsoft customers and market share.