Devices featuring Apple's iOS mobile operating system lead all other mobile devices with 58.8 percent of mobile Web traffic in the U.S. Android is far behind, but still in second place with 19.9 percent. Next is "other" with 10.9 percent, and after that is Research In Motion with 10.4 percent, according to data released by Quantcast on Monday.
Though Android has a ways to go to catch up with Apple's iOS, Android is beginning to take some of that share as more devices featuring Google's mobile OS hit stores. From April to May, for example, iOS lost just under 1 percent share, while Android gained slightly more, 1.3 percent, according to Quantcast.
It's important to note, however, that Quantcast's data does not include mobile Web use from iPads. That's a fairly glaring omission since Apple has sold 2 million of the touch-screen tablets (mostly in the U.S.), which use essentially the same platform, during the months of April and May.
Even without that data, iOS is still in the lead. But it's clear that Android is gaining momentum with the release of devices like the Nexus One, HTC Evo, and Motorola Droid, and HTC Droid Incredible.
Apple very clearly feels the competition too. At WWDC last week, CEO Steve Jobs spent much of his two-hour keynote presentation giving a sales pitch to his developers on the viability of his mobile platform.
This post was updated at 1:30 p.m. PDT with the correct manufacturers of the Droid and Droid Incredible.