Keeping two or more copies of the same document synchronized with each other in real-time is a complex challenge. This paper describes the differential synchronization algorithm. Differential synchronization offers scalability, fault-tolerance, and responsive collaborative editing across an unreliable network. 1 Conventional Strategies The three most common approaches to synchronization are ownership, event passing and three-way merges. These methods are conceptually simple, but all have drawbacks. link to googletalk video and mobWrite sw