Carnac is an open-source utility designed for Windows that enhances presentations by overlaying keystrokes and mouse clicks on the screen. This tool is particularly valuable for developers and presenters, as it allows for a clear demonstration of keyboard shortcuts and actions during screencasts. The application features an invisible WPF window that displays key presses and shortcuts with customizable settings, including position, opacity, and font size, ensuring that users can tailor the display to their needs.

In addition to its primary functionality, Carnac utilizes Reactive Extensions (Rx) to effectively manage input streams, making the codebase a non-trivial example of this technology. Notable features include a silent mode that can be activated with Ctrl+Alt+P, keymaps specific to applications, and the ability to highlight mouse clicks. Installation is straightforward, often facilitated through Chocolatey or manual download, and it requires .NETto function.