http://uwb25d43nnzerbozmtviwn7unn7ku226tpsjyhy5n4st5cf3d4mtflqd.onion/posts/e2ee/index.html
Like all peer-to-peer communication, Cwtch requires synchronous communication, meaning that both people must be online at the same time. However, its server feature also allows asynchronous communication by providing offline delivery: "Cwtch contact to contact chat is fully peer to peer, which means if one peer is offline, you cannot chat, and there is no mechanism for multiple people to chat.