WinDirStat and Bytopsy are both free and open source disk space analyzers for Windows. Choose WinDirStat for its extra views and reports; choose Bytopsy if you also want to clean, update and maintain the PC from the same window.
Side by side
| Feature | Bytopsy | WinDirStat |
|---|---|---|
| Price | Free | Free |
| Licence | MIT | GNU GPL v3 or later |
| Treemap | Yes, with a folder list above it | Yes, plus sunburst and flame graph views |
| Search and filters | Size, age, type and wildcard syntax (such as *.mp4 >500M older:1y) | Name, size, type and owner |
| Duplicates | Yes: size, quick hash, then SHA-256; similar photos too | Yes, by content hash |
| Scan history and compare | Every scan kept; see what grew or shrank | Save and reopen scan snapshots |
| Safe cleanup with protection rules | Yes: Blocked, Important and Caution levels, Recycle Bin, restore journal | Cleanup tools |
| WSL and Docker virtual disks | Shows and compacts them | Not a feature |
| Drivers, app updates, startup, uninstall with leftovers | Yes | No |
| Terminal app | bytopsy-cli, ncdu-style, exports ncdu-compatible JSON | No |
| Permission inspection, file recovery | No | Yes |
WinDirStat details from windirstat.net, October 2026. Something out of date? Tell us.
When WinDirStat is the better pick
- You want a long-established, single-purpose tool and nothing else on the machine.
- You need to inspect file permissions or try to recover deleted files on NTFS, exFAT and FAT.
- You like the sunburst or flame graph views, or the report exports and scan automation it offers.
- You prefer the GPL for its terms.
When Bytopsy fits better
- You want to act on what you find. Cleanup is built in, with every item measured first and checked against protection rules. Deletes are undoable.
- You look after other people's PCs. It is two self-contained
.exefiles with no installer and no runtime. Add abytopsy.portablefile and everything stays on the USB stick. The terminal version works over SSH. - You use WSL, Docker or local AI models. Their large disks and model caches have their own views.
- You want permissive licensing. MIT allows use at home, at work and on clients' PCs, and in your own tools.
Why not use both?
You can. Both are free and neither needs an installer. Bytopsy also reads and writes ncdu-compatible JSON, so a scan from the terminal or from a Linux machine opens in the windowed app. Download Bytopsy or read the guide to finding what fills your C: drive with any analyzer.