Existing tools for screen sharing and remote control only allow a single user to interact with a system while others are watching. Collaborative editors and whiteboards allow multiple users to work simultaneously, but only offer a limited set of tools. With CoShare, we combine both concepts into a screen sharing tool that gives remote viewers a mouse pointer and a text cursor so that they can seamlessly collaborate within the same desktop environment. We have developed a proof-of-concept implementation that leverages Linux’ multi-pointer support so users can control applications in parallel. It also allows limited sharing of clipboard and dragging files from the remote viewer’s desktop into the video-streamed desktop. In focus groups we gathered user requirements regarding privacy, control, and communication. A qualitative lab study identified further areas for improvement and demonstrated CoShare’s utility.