The quick answer
- You want the fastest scan: WizTree.
- You think in folders, not pictures: TreeSize Free.
- You want a portable treemap with strong filters: SpaceSniffer.
- You want free, open source, several views and a review step before anything is removed: freedisk.space, or WinDirStat itself.
Start with WinDirStat itself
WinDirStat is the classic. It draws a treemap where every file is a rectangle, area shows size and color shows file type. It is free and open source under the GPL v3.
It is also not abandoned. The project's releases page shows version 2.9.3, published on October 11, 2026. According to the official site, recent versions add largest-files, file-type, sunburst and flame graph views, cleanup actions, and faster scans of local NTFS, exFAT and FAT drives when run with administrator rights.
If you last used WinDirStat years ago and remember it as slow, try the current version before you switch.
The alternatives
WizTree
WizTree is known for speed, and it earns it. Instead of walking every folder, it reads the NTFS Master File Table directly, which is why a full drive often scans in seconds. It shows a folder tree, a treemap, a largest-files list and duplicate files, and it can export to CSV. It counts hard-linked files once, so its totals match what Windows reports.
Per its official site, WizTree is free for personal use. Commercial use needs a paid Supporter Code, and large organizations need an Enterprise license. The site does not list the price on its front page, so check the developer's site for current pricing. Version 4.33 came out on September 16, 2026, and there is now a Mac version too.
It is closed source.
TreeSize Free
TreeSize, from JAM Software, shows your drive as an Explorer-style folder tree sorted by size, with a treemap chart and PDF reports. It feels familiar if you already live in File Explorer.
The free edition is for private, non-commercial use on desktop Windows, and can't be used on servers. Features like duplicate search, disk usage comparison over time and scheduled scans are in the paid editions. On the TreeSize Free page in October 2026, TreeSize Personal was listed at €20.40 per user per year and TreeSize Professional from €41.00 per user per year, billed annually. Check the developer's site for current pricing.
SpaceSniffer
SpaceSniffer, from Uderzo Software, draws a treemap you navigate by zooming. Click a block to see inside it, double-click to zoom in. Its filters are a strength: you can combine type, size and age in one line, such as *.jpg;>1mb;<3months, and tag files with colors to come back to later.
It is freeware and portable, so there is nothing to install. The official page lists version 2.2.0.27. Donations are welcome. It is closed source.
freedisk.space for Windows
This is our app, so weigh this section with that in mind. It is free and open source under the MIT license, a native Windows app for Windows 10 and 11 on x64. The current release is version 0.2.3, delivered as a single .exe of about 174 MB with .NET built in, so there is nothing else to install.
It asks for administrator access every time it opens. That is what lets it read the NTFS file table directly, the same approach WizTree uses. On a 1 TB NVMe system drive with about 8 million items, a full scan took about 9 seconds in our tests. Without that access, or on drives that aren't NTFS, it falls back to a slower folder walk.
One scan feeds a treemap plus six other views, including sunburst, flame, bubbles, mind map and an age map. There is content-based duplicate detection, a Developer page for build folders and package caches, and an Applications page that finds leftovers in your AppData folders. A Ctrl+K search finds files by name as you type.
Cleanup is staged. You add items to a Cleanup list, confirm, and they move to the Recycle Bin. You can Put Back from inside the app. Core Windows folders like C:\Windows, Program Files and System Volume Information are blocked from cleanup entirely. There is one exception to the Recycle Bin rule: when Windows refuses an item as too big for the Recycle Bin, the app can delete it permanently, but only for things that rebuild on their own, like node_modules, build output and package caches, and only after you confirm them in a separate dialog.
It runs fully offline, with no account and no telemetry. The honest limits: it is a young project with a short track record, and Windows SmartScreen may warn you the first time you open it. Choose More info, then Run anyway.
Side by side
| App | Price | License | Main views | Fast MFT scan | Notes |
|---|---|---|---|---|---|
| WinDirStat | Free | Open (GPL v3) | Treemap, file types, sunburst, flame graph | Faster when elevated | Updated October 2026 |
| WizTree | Free for personal use; paid for commercial use | Closed | Tree, treemap, largest files, duplicates | Yes | Also on Mac |
| TreeSize Free | Free for private use; paid editions per user per year | Closed | Folder tree, treemap chart | Check the developer's site | Not for servers |
| SpaceSniffer | Free | Closed (freeware) | Zoomable treemap | Check the developer's site | Portable, strong filters |
| freedisk.space | Free | Open (MIT) | Treemap plus six other views, duplicates, developer files | Yes, with admin access | Recycle Bin cleanup list, young project |
Prices and versions were checked on each developer's site in October 2026.
What to look for
Scan speed
Tools that read the Master File Table, like WizTree and freedisk.space with admin access, are much faster on NTFS drives than tools that walk each folder. If you scan often or have a large drive, this matters most.
Honest sizes
Windows uses hard links heavily, especially in C:\Windows\WinSxS. A tool that counts each link separately will overstate how much space Windows takes. Our Windows 11 storage guide explains how to get the real WinSxS size with DISM.
What delete does
Check whether a tool sends items to the Recycle Bin or deletes them permanently, and whether it stops you from touching system folders. A visible list you confirm before anything moves is the safest setup.
Licensing
If you are using a tool at work, read the license. WizTree and TreeSize Free both require a paid license for commercial use. WinDirStat and freedisk.space are open source and free for any use.
How to choose
If WinDirStat works for you, the current version is a good tool and you can stay. If speed is what you want, WizTree is hard to beat. If you prefer folders, try TreeSize Free. If you want a portable treemap you can filter hard, use SpaceSniffer. If you want open source, many views of one scan, developer cleanup and a Recycle Bin safety net, try freedisk.space.
Clearing out old JavaScript projects? See how to find and delete node_modules.
Questions people ask
- Is WinDirStat still maintained?
- Yes. Version 2.9.3 was released in October 2026, and recent versions add sunburst and flame graph views and faster scans when run as administrator.
- Is WizTree faster than WinDirStat?
- Usually, on NTFS drives. WizTree reads the Master File Table directly instead of walking every folder, so a full drive often scans in seconds.
- Is WizTree free?
- WizTree is free for personal use. Commercial use needs a paid Supporter Code or an Enterprise license, so check the developer's site for current pricing.
- Can I use TreeSize Free at work?
- No. TreeSize Free is for private, non-commercial use on desktop Windows. Business and server use need TreeSize Personal or Professional.
- What is the best free open source disk analyzer for Windows?
- WinDirStat and freedisk.space are both free and open source. WinDirStat has the longer track record, and freedisk.space adds more views, duplicate and developer-file pages and a Recycle Bin cleanup list.
- Why does my disk analyzer need administrator rights?
- Reading the NTFS Master File Table directly requires administrator access. Without it, tools fall back to walking each folder, which is slower and can skip folders you don't have permission to read.