SoundCloud, the up-and-coming social audio publishing platform, is endorsing HTML5’s role in the future of the Web. Today, the Berlin-based startup is officially rolling out its HTML5 audio player as the service’s default, knocking the original, Flash-based player from that esteemed position.

The new player first went into beta in November, giving those curious enough an opportunity to experiment with it. Now that the bugs have been ironed out and a few new features added, the widget is ready for prime time.

Indeed, the service has been growing rapidly. Just this week, it surpassed 10 million registered users, a milestone that came just weeks after receiving a reported $50 million round of funding.

A big part of that growth, cofounder Alex Liung told us, is the company’s mobile strategy. It has highly functional native apps for iOS and Android, but the browser-based Web is another story. When users try to play back embedded SoundCloud clips on an iPad or iPhone, the old player simply wouldn’t work, like all the other Flash embeds scattered across the Web.

HTML5: A Necessary Move

For this reason, the conversion to an HTML5 embeddable player is a necessity for a service like SoundCloud if it expects to maximize its reach across the Web and keep growing. Flash will presumably never be supported on iOS devices iPads and iPhones, a fact that wouldn’t matter so much if Apple didn’t keep selling millions upon millions of them. Just last quarter, over 15 million iPads and 37 million iPhones landed in the hands of consumers, and this revolution in personal computing is still well underway. In November, Adobe announced that it would suspend development of the mobile version of Flash, apparently accepting that open standards like HTML5 and related technologies could do most of what Flash was capable of it.

It’s not just cross-device compatibility that makes ditching Flash a good idea. HTML5 is also less resource-intensive when playing back audio, and should exhibit better performance.

While testing the new player out, the SoundCloud team discovered a few other advantages as well. Apparently, the appearance of the revised player made users twice as likely to hit the “play” button. From there, they were eight times more likely to share a given track with others.

Now that it’s coming out of beta, the new player now supports saving any sound to one’s “likes” and making comments in-line on the waveform, which was one of more the powerful features of the original Flash player.