TreeSize Troubleshooting on Windows

Folder sizes show zero or stay empty

Cause: the scan hasn't reached that branch yet, or the account running TreeSize has no read access to it at all — a zero can mean 'nothing found' or 'nothing could be read,' and the interface doesn't always distinguish the two clearly.

Fix: wait for the scan to complete before judging any single folder, then check the same folder's permissions in its Properties > Security tab. If your account lacks read access, either grant it or rescan elevated.

"Access denied" appears on parts of the tree

Cause: Windows permissions block the scanning account from reading certain folders — common with other users' profile folders, system folders, and some cloud-sync directories.

Fix: run the scan as an administrator to cover most system-level cases. For folders owned by another user account, you'll need to take ownership or be granted access explicitly in Windows before any scanner can read them — no software workaround bypasses NTFS permissions.

Scan is extremely slow

Cause: commonly a very large number of small files (an inbox archive, a source code tree with thousands of files), a network path with high latency, or a security product scanning every file TreeSize touches in real time.

Fix: scan a narrower folder first to confirm the tool itself is working, then scope up. On a network share, expect scans to be slower than local drives regardless of software — see scanning a network drive for what's normal versus what's stuck. If antivirus real-time scanning is the bottleneck, that's a security-software setting, not a TreeSize setting, and changing it is a judgment call for whoever manages that machine.

Totals don't match File Explorer's Properties dialog

Cause: File Explorer's Properties dialog and TreeSize can both report either logical size or size-on-disk, and they don't always default to the same one. A mismatch of a few percent on a folder with many small files is usually cluster slack, not an error.

Fix: check which size mode each tool is showing and compare like with like. If the gap is large and not explained by allocation rounding, check for hidden or system files that one tool includes and the other's view settings exclude.

Totals don't match the drive's reported free space

Cause: a scan of user-visible folders will never account for every byte on a Windows system drive. The page file, hibernation file, System Restore points, Volume Shadow Copy data, and Windows' reserved storage all consume space without living inside a single scannable folder.

Fix: treat the scan as an explanation of the user-data portion of the drive, not a full reconciliation of every byte Windows reports. Our comparison with Windows' own storage settings explains where the two views diverge.

Network share scan stops partway through

Cause: a dropped connection, a permission boundary partway into the share, or the server timing out a long-running enumeration from a single session.

Fix: confirm the mapped drive or UNC path is still connected, re-authenticate if the session expired, and try scanning a subfolder of the share directly rather than the whole share at once. Details on setting this up correctly are in scanning a network drive with TreeSize.

A OneDrive folder shows unexpected sizes

Cause: files set to "free up space" in OneDrive are placeholders on disk — the file system reports a size for them, but the actual bytes live in the cloud, not locally. Depending on how a scanner reads file metadata, these can show their full cloud size, a near-zero local size, or something in between.

Fix: don't use a folder-size scan alone to judge how much local disk space OneDrive files are using. Check a file's OneDrive status icon (cloud, checkmark, or solid) to see whether it's a placeholder or stored locally before drawing conclusions from size figures.

The program won't start, or the context-menu entry is missing

Cause: an interrupted installation, a portable copy missing a required file, or Windows Explorer needing a restart after installation for the context-menu entry to register.

Fix: sign out and back in, or restart Explorer, and check whether the shortcut points to a file that still exists. If a portable build won't launch at all, re-download it — a partial or corrupted download is the most common cause. General setup steps are covered in how to use TreeSize, and safety questions around installers belong on is TreeSize safe.