After more than two years of work, Mozilla has scrapped its effort to build a Metro-specific version of Firefox for Windows 8, saying that users have shown almost no interest.

Microsoft designed what it previously called the Metro interface for touch-screen devices like tablets and introduced it with Windows 8 along with a version of Internet Explorer designed to run on it. Two years ago, after winning a debate with Microsoft over whether it even could be possible to bring a modern third-party browser to Metro, Mozilla embarked on its Firefox for Metro journey.

Now it's over for now, though Firefox will mothball the code in case it needs to change its mind.

"As the team built and tested and refined the product, we've been watching Metro's adoption. From what we can see, it's pretty flat," said Johnathan Nightingale, vice president of Firefox, in a blog post Friday. "On any given day we have, for instance, millions of people testing pre-release versions of Firefox desktop, but we've never seen more than 1,000 active daily users in the Metro environment."

Mozilla opted to drop it for now rather than risk shipping something that's poorly tested but that must be supported for years.

"When I talk about the need to pick our battles, this feels like a bad one to pick: significant investment and low impact," Nightingale said.

The move is a vote of no confidence for Microsoft's new interface from a prominent software developer. Microsoft, eager to move to the touch-screen era after being caught flat-footed by Apple's iPhone and iPad, gave Windows dual interfaces -- some would say dueling, since they're so different and customers have found the transition so difficult.