Most QDirStat problems can be narrowed down by testing a small local directory, launching from a terminal and confirming that the same user account can read the target path outside the application.
Avoid changing several variables at once. A simple comparison between one working folder and one failing folder usually reveals whether the issue involves permissions, a mount, storage performance or the application environment.
QDirStat does not launch
Read terminal output
A terminal launch can reveal a missing Qt plugin, library mismatch, display-session error or invalid configuration.
Confirm package integrity
Use your distribution package manager to verify or reinstall the package rather than copying individual libraries into system folders.
Test the user profile
A new or temporary user configuration can help distinguish a global installation issue from a damaged personal setting.
The scan is extremely slow
Check the storage type
Network filesystems, hard drives waking from sleep and directories with millions of entries can take much longer than a local SSD folder.
Reduce the scan root
Select the suspected directory instead of the entire filesystem.
Watch other disk activity
Backups, indexing and package updates can compete for the same storage device.
Folders are missing or unreadable
Test shell access
List the directory as the same user. If the shell cannot read it, QDirStat will not bypass that restriction.
Inspect mount state
Confirm the filesystem is mounted and credentials or ownership options are valid.
Accept intentional boundaries
Protected paths may be irrelevant to the storage problem and do not always justify a root session.
Totals do not match df or a storage panel
Compare what each tool measures
Directory analyzers count accessible files. Filesystem tools can report reserved blocks, snapshots, metadata and deleted files still held open by processes.
Look for separate mounts
A directory tree can cross or exclude mount boundaries depending on the selected path and configuration.
Check for stale cache data
A cache file reports an earlier state and should not be compared as though it were a live scan.
Next steps
Return to the main QDirStat page for the source archive, compatibility summary and twenty-question FAQ, or continue with a related guide below.