An earlier video calling app from Google for Android and iOS mobile devices. Introduced in 2016 to compete with FaceTime and WhatsApp, Google Duo was replaced with Google Meet in 2022. Duo was noted for its simplicity and automatic switching between cellular and Wi-Fi. It was designed to provide good visual quality over slow networks, and it supported end-to-end encryption. Duo's "Knock Knock" feature displayed the caller before the recipient answered. See
videoconferencing and
Google Meet.