Seth Rosenblatt/CNET

A key part of Google's plans to build the future of its Chromecast dongle has slipped into place as the company unlocked its Chromecast software development kit on Monday morning.

The Google Cast Software Development Kit (SDK), available now, will allow app developers to give their users the option to stream their apps or Web sites to the Chromecast, which acts like a receiver that you plug into your TV's HDMI port. Web site compatibility only works in Google Chrome via extension, also available today.

The Cast SDK has been available previously only in restricted form, with Google working with well-known companies such as HBO, Pandora, and Netflix to prove the device's worth. Now that it's open to all, developers will be able to register devices and apps for testing and publishing. Once the Cast SDK has been integrated with an app, current users can get the updated app through their regular app marketplace.

Chromecast's future depends on developers making their apps compatible with the device.

"With the Chromecast, we're resetting consumer applications," said Rishi Chandra, Chromecast's director of product management. People, he said, "should expect their phones or tablet applications to just work on the television."

That's a major change for people on both the development and user ends of the app. If the Chromecast's upward trajectory continues, you can bet it will play a big role in Google's desire to get on all your screens.

Chromecast's limited development has thus far demonstrated only a small part of its potential, tapping into video, music, and local media applications like RealPlayer Cloud. Its future, said Chandra, depends on developers.

"Gaming is an exciting opportunity for what you can do with Chromecast," he said, as one example of an area where developers could spend more time. "It's exactly the right model. The fact that it works with your iOS phone and Android tablet and Windows laptop is true multiscreen. There's a lot of potential there," he said.

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As simple as the Chromecast is, making sure that it was easy to develop for took some time. One thing Google learned, said Chandra, is that Chromecast developers are like Chromecast consumers: they want it to just work.

When it comes to the SDK, he said that "developers don't really need or want all the features. They want turnkey solutions."

When it comes to all things Chromecast, the geniuses at Google may have finally learned their lesson: keep it simple, stupid.

Updated at 1:57 p.m. PT: to specify the RealPlayer app as RealPlayer Cloud.

Corrected at 11:15 a.m.: to change the day that Google made its announcement to Monday, February 3.