Every hard disk, however large it may be, is filled up to capacity after some time. Then it's about time to find out where all that disk space has gone, and to reclaim some of it.
This is what KDirStat was all about. The original KDirStat was a KDE 3 application. Now, there is the brand-new QDirStat, based on the same code, but with most of it rewritten with newer technology based on the latest Qt 5. It no longer depends on KDE; rather, it's now desktop agnostic, running just as well under GNOME, Xfce and all thoser other X11-based Linux/BSD desktops.
Aside from the up-to-date underlying framework, QDirStat has a number of new features compared to KDirStat. To name a few:
Multi-selection in both the tree and the treemap.
Unlimited number of user-defined cleanup actions.
Properly show errors of cleanup actions (and their output, if desired).
File categories (MIME types) and their treemap color are now configurable.
Exclude rules for directories are easily configurable.
Desktop-agnostic; no longer relies on KDE or any other specific desktop.
QDirStat main window (notice the multi-selection in the tree and in the treemap)
Output during cleanup actions.
This window is purely optional. It can be configured to be shown when there is error output (shown red), if a cleanup action takes longer than a configurable amount of time, always, or never.
For more details, more screenshots and ready-made packages, see