Collaborative editing of electronic documents in realtime is provided. A host serves a client code over a network to a plurality of clients that each employ a browser to run the client code. The client code revises the text document locally in response to user input, frequently sends those edits to the host, receives updates from the other clients via the host, and revises the local text document accordingly. Each client, in some embodiments, stores three variables, one for edits not yet reported to the host, one for edits reported by not yet acknowledged, and one for the text document as modified by the acknowledged edits. Updates from the other clients are applied to the three variables according to certain rules. A composition of the three variables yields a version of the text document. The host keeps records of which edits were introduced by which client.