Google Has Launched A New Video-Calling App Called Duo, In A Direct Challenge To Skype And Apple Facetime.

First announced at the Google I/O developer conference in May, Duo is a one-to-one video calling app.

Like WhatsApp, it works using your mobile number, so once you've downloaded the app and logged in using a Google account, you can immediately video call anyone on your contacts list that also has the app.

The advantage of Duo over FaceTime is that it works on both Android and iOS, whereas FaceTime only works on Apple devices. It is also designed to be simpler than Skype , allowing users to begin a video call with a single tap.

"Video calling is the next best thing to being with someone in person, but too often it can be a frustrating or complicated experience," said Justin Uberti, principal software engineer at Google, in a blog post.

"You shouldn't have to worry about whether your call will connect, or if your friend is using the same type of device as you are. It’s no wonder that nearly half of us never make video call. While Google's primary focus is on simplicity, it does have a couple of features to help differentiate it from its competitors.

For example, a feature called Knock Knock lets you see live video of your caller before you answer, giving you a sense of what they’re up to and why they want to chat.

Google says this makes video calls feel like "an invitation rather than an interruption"

Another useful feature is the ability to switch between Wi-Fi and cellular data automatically without dropping your call - so you can start your call at home, and continue seamlessly when you head out the door.

In the background, Google has also built Duo to work to cope with slower networks such as 2G, and with end-to-end encryption for security.

Google is beginning to roll out Duo for Android and iOS today, and it will be live worldwide in the next few days.