Duo is a video chat mobile app developed by Google, available on both Android and iOS. Google Duo will replace Hangouts for video calling within the suite of Googles apps.

Features:

• HD 720p video
• Optimized for low bandwidth mobile networks. The app optimizes WebRTC and uses QUIC over UDP. Optimisation is further achieved through the degradation of video quality through monitoring network quality.
• “Knock Knock” – an Android-only feature which shows a live preview of the caller before the recipient picks up, which Google says is to “make calls feel more like an invitation rather than an interruption”
• End-to-end encryption by default,
• Google Assistant support,
• Use of phone numbers to allow users to easily call people from their contact list,
• Automatic switching between WiFi and mobile data.