Mathematica Online operates completely in the cloud and is accessible through any modern Web browser, with no installation or configuration required, and is completely interoperable with Mathematicaon the desktop. Users can simply point a Web browser at Mathematica Online, then log in, and immediately start to use the Mathematica notebook interface, just like on the desktop. A computable document can be built up interactively, mixing text, code, graphics, and so on — with inputs that can be immediately run. Files are stored in the cloud and can be accessed from anywhere, and users can make any online document accessible to anyone they designate.