Find What's Taking Up Space on Your Drive

Windows tells you a drive is full, but not what filled it. Each tool below scans a drive and sorts every folder by size, so the culprit — an old game, a forgotten video export, a bloated cache — sits at the top of the list. All three are free for home use and install from their developers' own sites.

For most people

TreeSize Free

Folder tree sorted by size, from JAM Software.

The easiest to read: it looks like File Explorer, with each folder's size and percentage next to its name. Expand the biggest folder, then the biggest one inside it, and keep going until you find what to delete. The catch is that the free edition is for personal use only, and the installer and app nudge you toward the paid editions.

If you want it fast

WizTree

Reads the drive's file table directly, so a full scan takes seconds.

Much faster than the others on a large drive, and it adds a colored block map where the biggest rectangles are the biggest files. Free for personal use; a business needs a paid license. The speed trick only works on NTFS drives, which covers almost every Windows system drive, but USB sticks and some external drives scan at normal speed.

If you want open source

WinDirStat

The original disk usage treemap, free and open source.

Pick this if you want software with no commercial edition at all. It is slower to scan than WizTree, but shows the same kind of block map and lets you delete files from inside the app.

If you only pick one

Start with TreeSize Free. The folder list is the fastest way to answer "what is using my space?" without learning anything new.

What to avoid

• Deleting anything inside C:\Windows — a folder like WinSxS looks huge but is partly shared files counted twice. Use Settings > System > Storage > Cleanup recommendations instead.
• "PC cleaner" apps that promise to free gigabytes with one click. They mostly clear temporary files Windows would clear anyway, and many bundle extra software or push a subscription.