Mozilla accuses Microsoft of anticompetitive behavior with Windows RT

'Trying to lock out competing browsers' on Windows RT's 'desktop,' says Firefox director

Mozilla yesterday accused Microsoft of withholding APIs necessary to build a competitive browser for Windows RT, and said the behavior "may have antitrust implications."

Harvey Anderson, Mozilla's general counsel, and Asa Dotzler, director of Firefox, weighed in with the accusations late Wednesday in a pair of blog posts.

Anderson warned that Microsoft's decision to allow only Internet Explorer 10 (IE10) in one mode of Windows RT "signal[s] an unwelcome return to the digital dark ages where users and developers didn't have browser choices."

Dotlzer was more direct. "Microsoft is trying to lock out competing browsers when it comes to Windows running on ARM chips," he said.

Their beef stems from Microsoft's decision to deny other browser makers, including Mozilla, access to APIs (application programming interfaces) necessary to run a browser on Windows RT's conventional desktop.

Windows RT -- the edition for ARM processors -- will offer a Metro mode that features touch-based apps available from the Windows Store. But it also includes a heavily-restricted "desktop" mode that will run only Microsoft code.

Among the software that will run on the Windows RT desktop -- Microsoft hasn't given that mode a specific name -- will be new versions of Office's Word, Excel, PowerPoint and OneNote; the Windows Explorer file manager; and a "desktop" edition of Internet Explorer 10 (IE10).

"[Windows RT] supports the Windows desktop experience including File Explorer, Internet Explorer 10 for the desktop, and most other intrinsic Windows desktop features -- which have been significantly architected for both touch and minimized power/resource consumption," said Steven Sinofsky, Microsoft's top Windows executive, earlier this year in the company's first detailed description of the new tablet OS.

Sinofsky's comments were interpreted to mean that the RT desktop mode was off limits to other vendors' code.

And that's what raised hackles at Mozilla.

"Windows on ARM [the former name for Windows RT] prohibits any browser except for Internet Explorer from running in the privileged 'Windows Classic' environment," said Anderson. "In practice, this means that only Internet Explorer will be able to perform many of the advanced computing functions vital to modern browsers in terms of speed, stability, and security to which users have grown accustomed."

Dotzler was clearer in describing how Mozilla sees Microsoft hindering browser rivals.

"On ARM chips, Microsoft gives IE access [to] special APIs absolutely necessary for building a modern browser that it won't give to other browsers, so there's no way another browser can possibly compete with IE in terms of features or performance," said Dotzler.

He did not spell out those APIs or how Microsoft was limiting access to them, but in a follow-up post on his personal blog today, Dotzler elaborated.

"It's not precisely 'running a browser in Classic' that matters for Windows on ARM," Dotzler said. "It's that running a browser in Classic is the only way that Microsoft has allowed us to get access to the APIs that a browser needs to deliver modern capabilities and performance in Classic and Metro. A browser running exclusively in Metro does not have the APIs necessary to compete with IE or any other modern browser."

As Dotzler inferred, there's nothing blocking Mozilla from submitting a Metro version of Firefox to the Windows Store. A company spokeswoman confirmed that late Wednesday.

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