TreeSize Free is a Windows disk analyzer from JAM Software that scans your drives and shows a sortable, expandable tree of every folder with exact sizes and percentages — the Windows answer to DaisyDisk on macOS. It's safe and legitimate: JAM Software is an established German developer, the free version has no bundled adware, and TreeSize only reads and deletes what you tell it to. The short version: download it from jam-software.com, run it as administrator, scan your C: drive, sort by size, then drill into the largest folders and delete what you don't need.
TL;DR
- TreeSize Free is a free Windows disk-space analyzer that maps folder sizes in one scan.
- Run it as administrator or it silently skips system folders and undercounts.
- Sort by the Size column and expand the biggest folders to find what's worth deleting.
- Safe to clear: Downloads, Temp, app caches,
Windows.old, old game installs. - Leave alone:
WinSxS,System32, andProgramDatafor apps you still use.
What is TreeSize Free?
TreeSize Free is a lightweight disk-usage analyzer that walks an entire drive and calculates every folder's size in a single pass, then displays the whole tree sorted largest-first. File Explorer can't do this, it only shows a folder's size when you right-click Properties on each one individually. TreeSize is free for personal use; paid Personal and Professional editions add scheduled scans, duplicate finders, and bulk export. It runs from a standard installer or as a portable ZIP, and reads NTFS permissions correctly when launched with admin rights.
Why use TreeSize instead of File Explorer?
The core problem TreeSize solves is visibility. Here's how the two compare:
| Capability | File Explorer | TreeSize Free |
|---|---|---|
| Folder sizes at a glance | No, right-click Properties one by one | Yes, whole tree in one scan |
| Sort folders by size | No | Yes |
| See into system/hidden folders | Limited | Yes, when run as administrator |
| Delete from within the tool | No | Yes, sends to Recycle Bin |
| Cost | Built in | Free for personal use |
That one-pass, sorted view is why TreeSize is the default free analyzer most Windows users reach for.
How do I use TreeSize Free safely?
Follow these steps in order:
- Download TreeSize Free from the official jam-software.com site.
- Install with default options, or extract the portable version.
- Right-click TreeSize and choose Run as administrator, without this, results under
C:\Windows, other users' folders, andProgramDataare incomplete. - Click Select Directory › Select Drive › C:.
- Wait for the scan, typically 2–10 minutes for a 1 TB drive.
- Click the Size column header to sort largest-first.
- Expand the biggest folders with the + next to each row.
- Drill in until you find a specific file or subfolder worth removing.
- Right-click and choose Delete (sends to Recycle Bin), or Open in Explorer to handle it manually.
What is safe to delete, and what should I leave alone?
TreeSize shows you everything, including files Windows depends on, so knowing what to touch matters.
Safe to target: C:\Users\<you>\Downloads, %localappdata%\Temp, an app's Cache subfolder under %localappdata%, C:\Windows.old (the leftover from a Windows upgrade), and old game install folders.
Leave alone: C:\Windows\WinSxS (the component store, which looks huge but is managed by Windows), C:\Windows\System32, ProgramData folders for apps you still use, and $Recycle.Bin (empty it from the desktop Recycle Bin icon instead). Because TreeSize deletes to the Recycle Bin by default, an accidental deletion of a personal file is recoverable, but system folders should never be removed by hand.
Where to go next
If you'd rather not install anything, the native route covers most cleanups, see deep cleaning Windows 11 and 10 without third-party utilities. To understand the biggest folders TreeSize surfaces, read what the AppData folder is and whether you can delete it, why OneDrive takes up local hard drive space, and how to safely empty the Downloads folder on PC. To reclaim large blocks fast, see how to uninstall heavy PC games properly.
Related: what actually fills up phone storage in 2026
FAQ
Is TreeSize Free actually free?
Yes, TreeSize Free is free for personal use. JAM Software also sells paid Personal and Professional editions that add features like scheduled scans, duplicate finders, and bulk export, but the free version is enough to map and clean a drive.
Why do I need to run TreeSize as administrator?
Running TreeSize as administrator lets it read protected system folders like C:\Windows and ProgramData. Without admin rights it silently skips those areas, so its totals undercount your real disk usage.
Is it safe to delete files from within TreeSize?
Deleting personal files from TreeSize is safe because it sends them to the Recycle Bin by default, so they're recoverable. Never delete system folders such as WinSxS or System32, even though they look large.
How long does a TreeSize scan take?
A TreeSize scan of a typical 1 TB drive takes about 2–10 minutes, depending on file count and disk speed. SSDs scan considerably faster than mechanical hard drives.
Is TreeSize Free safe to use?
Yes. TreeSize Free is a clean, well-established tool from JAM Software with no adware in the official build, so download it only from jam-software.com. It deletes files to the Recycle Bin by default, so accidental deletions of personal files are recoverable — just never remove protected system folders like WinSxS or System32 by hand.
TreeSize vs CCleaner — which should I use?
They do different jobs. TreeSize shows you where space went so you decide what to delete; CCleaner auto-cleans caches and temp files by category. TreeSize is the better choice when you want to find a specific large folder or file; CCleaner is faster for routine junk clearing but makes more decisions for you. For a one-off "what's eating my disk?" question, TreeSize is the safer, more transparent option.
On your phone, Cleanor gives you the same kind of size-first visibility plus safe, local one-tap cleanup, with nothing uploaded. See how Cleanor frees up phone storage or get the Cleanor app.