WinDirStat (Windows Directory Statistics) is a disk usage statistics viewer and cleanup tool for Microsoft Windows. It provides a graphical representation of disk usage, displaying how much space each file and folder consumes. The application shows directory trees, subdirectory sizes, and file types, using a color-coded treemap to make it easy to identify large files and directories. This helps users manage their disk space more efficiently by identifying and removing unnecessary files. WinDirStat is open-source and has been praised for its simplicity, visual appeal, and effectiveness in disk space management.