TreeSize Free: Find What Is Using Disk Space on Windows

TreeSize Free is a Windows disk-space analyzer from JAM Software. It scans a drive or folder, calculates the space used beneath each directory, and presents the results as an expandable tree. This makes it easier to find large folders than checking each folder's Properties window in File Explorer.

TreeSize identifies where storage is being used; it does not decide whether a file is safe to remove. Review every item before deleting it, and use Windows or the relevant application's own cleanup tools for system and managed data.

What TreeSize Free is useful for

• Finding folders that use the most space on a drive.
• Expanding a large folder to trace storage use to a subfolder.
• Sorting scan results by size, allocated space, file count, or other available columns.
• Opening a result in File Explorer so you can inspect it normally.
• Scanning a specific folder, removable drive, or other supported location.

Paid TreeSize editions add features beyond the Free edition. Because product packaging changes, compare the current edition descriptions before choosing based on a particular export, duplicate-search, automation, or reporting feature.

TreeSize Free versus File Explorer

How to scan a drive with TreeSize Free

1. Download TreeSize Free from JAM Software's official source or a trusted software channel.
2. Install it, or use the official portable edition if one is offered for your selected version.
3. Open TreeSize and choose Select Directory, then select the drive or folder to inspect.
4. Wait for the scan to finish. The time depends on the number of files, storage type, permissions, and current system activity.
5. Sort by Size or Allocated space, depending on the question you are investigating.
6. Expand the largest folder and continue down its largest subfolders.
7. Right-click a result and choose Open in Explorer before deleting anything unfamiliar.

Size versus allocated space

Size is the total logical size of the files. Allocated space reflects storage reserved on disk and may differ because of cluster size, compression, sparse files, or other filesystem behavior. If you are investigating why a drive is full, allocated space can be the more relevant column.

Results may also appear different from Windows Storage because applications use different counting rules, some files are inaccessible, and cloud placeholders may not occupy their full logical size locally.

When to run TreeSize as administrator

A normal scan may be unable to read other users' profiles and protected system locations. If the total looks incomplete and you are authorized to inspect the computer, close the app and use Run as administrator. Elevated access improves visibility but also increases the consequences of deleting the wrong item. Use it for diagnosis, not as permission to remove protected folders.

Items that are usually reasonable to review

• Personal downloads you recognize and no longer need.
• Old videos, installers, archives, virtual machines, and project exports.
• Duplicate personal files after opening and comparing them.
• Old game or application folders only after the related software has been uninstalled correctly.
• Application caches when that application provides a documented cleanup option.

Back up irreplaceable files before a large cleanup. If an item belongs to an installed application, uninstall or clean it from the application's settings rather than deleting its folder manually.

Do not manually delete these Windows folders

• C:WindowsSystem32
• C:WindowsWinSxS
• Unknown content under C:ProgramData
• Application folders under C:Program Files or C:Program Files (x86)
• Recovery, boot, installer, or driver folders

Do not manually delete Windows.old just because it is large. Use Settings > System > Storage > Temporary files or Windows' supported cleanup interface so that removal occurs safely. Keeping Windows.old for the available rollback period may also be useful after an upgrade.

A safe cleanup workflow

1. Use TreeSize only to locate the large branch.
2. Open the folder in File Explorer and identify who created the data.
3. Close applications that may be using it.
4. Use the app's uninstall, storage, or cleanup command when one exists.
5. Back up personal data, then delete only files you understand.
6. Leave items in the Recycle Bin until you confirm that Windows and your applications work normally.

TreeSize Free is most valuable as a map of disk usage. Treat it as a diagnostic tool, then use the safest owner-specific method to remove the data it helps you find.