Don't expect Firefox to surface on your Surface 2 or Windows 8.1 start screen, as the open-source software developer behind the browser has abandoned its Metro-styled app.

Mozilla realized launching the 1.0 version of its Microsoft Modern UI app "would be a mistake," wrote Johnathan Nightingale, vice president of Firefox, in a blog post.

"It looked like the next battleground for the web," noted Nightingale. Now he says, "we've been watching Metro's adoption. From what we can see, it's pretty flat."

While pre-release versions of Firefox's desktop browser are beta tested by millions of people, the company never saw more than 1,000 active daily users taking advantage of Metro.

If a bug exists in a Metro app, does anyone hear it?

The problem with Microsoft's new design language isn't just that it's unpopular; it's also hard for app developers to properly bug test their software.

Nightingale theorized that Mozilla could have eventually shipped the Firefox Metro app, but without real-world testing, a lot of glitches would have been discovered by end users.

This decision to pull the plug on this Mozilla app ends its arduous two-year development cycle. It was first announced in February 2012 and slated to finally release in December of last year.

It was even previewed just before the end of last year, but delayed as recently as January of this year and now won't come out any time soon.

Instead, Mozilla will focus on its development efforts on existing Firefox platforms, including Mac, Linux, Android and straight-up Windows.

Maybe when Windows 9 rolls around, it can consider giving Metro another go, but for now it says the real costs of investment in a platform its users have shown little sign of adopting isn't worth it.