Cloud9 is a client designed to run in a Web Browser without requiring additional software. Cloud9 is currently only a prototype, implemented using a Flash applet to connect to the server. Eventually the goal is to use the WHAT-WG WebApps Connection class and not require any applets.

Cloud9's interface is written entirely in HTML, CSS, and JavaScript. It supports the MudLink protocol exclusively, as MudLink was designed to be compatible with the NUL-terminated message structure used by both Flash and the proposed Connection JavaScript class.

By using HTML and CSS for the client's interface, the client can easily support highly dynamic and flexible client features, such as server-defined windows and "widgets," such as a paper-doll widget showing the status of the player's character, or a fancy navigation compass supporting unique navigation modes on the server.