Methods and apparatus, including computer program products, for a single keystroke file comparison tool. A first version of a file is downloaded from a repository to a client computer. An updated version of the file is downloaded from the repository to the client computer. State information for the file is stored. The state information specifies two versions of the file. In response to a single user input, a file comparison is performed on the file. The file comparison produces an output showing differences between the two versions specified by the state information for the file. The state information can be stored in a hyperlink that refers to the file. User input selecting the hyperlink invokes the file comparison on the file.