They're using websockets I believe.
Look in the network tab for .ws (hosted on Firebase). You can inspect the messages using Chrome. It sends updates for every change to a block you make.
A websocket? I'm assuming that once the websocket is open, any future traffic inside wouldn't be logged in the developer tools?
Websockets probably. The built JS contains references to both WebSocket and Firebase.
They're using websockets I believe.
Look in the network tab for .ws (hosted on Firebase). You can inspect the messages using Chrome. It sends updates for every change to a block you make.