Google has announced that its new FaceTime and Skype competitor, Duo, is available to download. With Duo, the aim is to make video calling as easy and reliable as possible. No complicated sign up procedure, no remembering usernames and no unintuitive user interfaces. 

Google first introduced its innovative new video calling app, Duo, in May at its I/O conference in San Francisco, and the company claims the app takes all of the complexity out of video calling. 

The entire user interface is designed to be intuitive and simple to use. Even the set up process is simple and requires just your phone number, according to the search engine giant. Once set up, a video call can be initiated with just a single tap. 

Part of the attraction of Duo is that Google built in the capability to stay online and connected even when you're on a slower network. The video quality is reduced "gracefully" to ensure that calls aren't disconnected, and don't break up. And you won't have to wait ages for the call to connect either. It's quick, regardless of your network's reliability. 

One of the most interesting features of Duo is Knock Knock, which lets you see a live video of your caller before you answer. Then to answer the call you slide up the icon and dive right in to the call without any interruption or delay. 

For those worried about security, Google says that all calls are end-to-end encrypted, so that no one can listen in on your calls. 

Duo is rolling out for Android and iOS from today, and will be live across the globe within the next few days. It's free to download and free to use, as with pretty much all of Google's services.