Google announced the launch of Duo, its new video calling app, to step up competition with Apple’s FaceTime, Facebook Messenger and Skype.

Duo, first revealed by Google at its I/O developer conference in May, is described as “a simple one-to-one calling app” and is available for both Android and iOS (unlike FaceTime).

Google already offers video calling through Hangouts, although this is seen to be increasingly positioned towards enterprise users.

In an official blog, Google was keen to talk up the app’s simplicity, only requiring a phone number to be used, and not a separate account.

It also said it had optimised Duo to connect video calls even when users are on slower networks, to address failed and dropped calls, with the capability to switch between Wi-Fi and mobile data when on the go.

“Call quality adjusts to changing network conditions to keep you connected – when bandwidth is limited, Google will gracefully reduce the resolution to keep the call going smoothly,” said the company.

With “an emphasis on privacy and security”, all Duo calls are also end to end encrypted.

Perhaps a big differentiator from FaceTime, Duo also supports a feature called Knock Knock, which enables users to see live video of the caller before answering, “giving you a sense of what they’re up to and why they want to chat”.

At its I/O developer conference, the company also announced Allo, an instant messaging app, which is yet to be released.