TreeSize Free is a Windows disk analyzer from JAM Software. It scans your drives and presents a sortable, expandable tree of folders with exact sizes and percentages — the native answer to DaisyDisk on macOS.

Short answer: download TreeSize Free from jam-software.com, run it as administrator, scan your C: drive, and sort by size. Expand the largest folders to find what is taking space, then delete from within TreeSize or send files to the Recycle Bin.

Why TreeSize is the default free analyzer on Windows

File Explorer does not show folder sizes without right-clicking Properties on each one. TreeSize walks the drive, calculates every folder size in one pass, and displays the whole tree sorted largest-first.

  • runs from a standard installer or portable ZIP
  • free for personal use (paid "Personal" and "Professional" editions add features like scheduled scans, duplicate finders, and bulk export)
  • reads NTFS permissions correctly when run as administrator — without that, it silently skips system folders

Using TreeSize safely

  1. download TreeSize Free from the official jam-software.com site
  2. install (default options are fine) or extract the portable version
  3. right-click TreeSize and choose Run as administrator — without admin, results under C:\Windows, C:\Users\<other-users>, and ProgramData are incomplete
  4. click Select Directory > Select Drive > C:
  5. wait for the scan — typically 2–10 minutes for a 1 TB drive
  6. click the Size column to sort
  7. expand the biggest folders by clicking the + next to each row
  8. drill in until you find a specific file or subfolder worth removing
  9. right-click and choose Delete (sends to Recycle Bin) — or open the folder in File Explorer via Open in Explorer

What to safely target: C:\Users\<you>\Downloads, %localappdata%\Temp, %localappdata%\<app>\Cache, C:\Windows.old, old game install folders.

What to leave alone: C:\Windows\WinSxS, C:\Windows\System32, ProgramData for apps you still use, $Recycle.Bin (empty via the desktop Recycle Bin icon instead).

Better next routes

If you want a direct replacement for CCleaner's one-click cleanup, read Best CCleaner Alternatives for Windows 11.

For the native-only path without downloading anything, continue with How to Find the Largest Files on Windows 11 Without Third-Party Apps.