The treemap represents each file as a colored rectangle, the area of which is proportional to the file's size. The extension list, which serves as a legend and shows statistics about the file types.The treemap, which shows the whole contents of the directory tree straight away,.The directory list, which resembles the tree view of the Windows Explorer but is sorted by file/subtree size,.On start up, it reads the whole directory tree once and then presents it in three useful views:

Please visit the WinDirStat blog for more up-to-date information about the program. Note: if you are looking for an alternative for Linux, you are looking for KDirStat ( apt-get install kdirstat or apt-get install k4dirstat on Debian-derivatives) or QDirStat and for MacOS X it would be Disk Inventory X or GrandPerspective.

WinDirStat is a disk usage statistics viewer and cleanup tool for various versions of Microsoft Windows. Latest version: 1.1.2 Windows Directory Statistics WinDirStat - Windows Directory Statistics

Win folder size