HTTP-upgraded bi-directional protocol (HTTP/1.1, not HTTP/2). Established via an HTTP GET with an Upgrade header to which the server replies HTTP 101 Switching Protocols, after which the socket carries WebSocket frames. Used as the browser-side transport in ManageIQ's in-browser remote consoles. Protocol underlying real-time web apps such as chat. Action Cable speaks WebSockets only, which excludes a small percentage of users on very old browsers lacking WebSocket support.