Surface computing encourages exploratory interaction, and many applications are designed to work this way. In essence, the user needs to be able to ask “What if?” This requires support for recording the history of such explorations and allowing reversion to earlier states. This paper reports on system for providing this support. As a first step, the theoretical basis for this approach to software is discussed, including direct manipulation, epistemic loops, and frameworks for sensemaking. Next, approaches to software support are presented, including undo facilities, browser back and forward buttons, and most importantly, source code management tools such as Subversion and Git. We then present our prototype software for providing support for version history management in web applications. We first illustrate usage of the software augmenting sample web applications. We then document the technical architecture, which uses JavaScript Proxy objects to maintain access to the application’s internal model. The Ra API is outlined, illustrating how Ra may be connected to an existing Web application with minimal code change; we also discuss limitations and workarounds.