Disk space analyzers for Windows, compared
SpaceSharp, WinDirStat, WizTree and TreeSize Free all answer the same question: what is taking up the space on this drive? Here is how they differ, taken from each product's own pages.
Free · open source · Windows 10 and 11 · facts checked 11 November 2026
In short
Which one fits you?
SpaceSharp
- A treemap with names on the boxes that you zoom into
- Compares each scan with the last and says what is safe to clear
- Open source, and free at home and at work
WinDirStat
- The long-standing open source choice, modernized in its 2.x releases
- Sunburst and flame graphs, command-line scans, JSON export
- Free at home and at work
WizTree
- Known for very fast scans and a sorted list of every file
- Scans several drives in one run
- Free for personal use; a paid code for work
TreeSize Free
- An Explorer-style tree with a size on every folder
- Duplicate search and scan comparison in the paid editions
- Free for private use; paid editions for work and servers
Side by side
Four disk space analyzers, one table
The free edition of each, as its own website describes it.
| Feature |  SpaceSharp | WinDirStat | WizTree | TreeSize Free |
|---|---|---|---|---|
| Free at home | Yes.Yes | Yes.Yes | Yes.Yes | Yes.Yes |
| Free at work | Yes.Yes | Yes.Yes | No.Needs a paid Supporter Code | No.Paid editions |
| Open source | Yes.MIT | Yes.GPL | No.Closed | No.Closed |
| Fast scan from the NTFS file table | Yes.As administrator | Yes.When elevated | Yes.As administrator | Not stated on its pages |
| Treemap | Yes.Names and sizes on the boxes; zoom, pan, minimap | Yes.Plus sunburst and flame graphs | Yes.Below the folder tree | Yes.A chart next to the tree |
| Duplicates compared by contents | Yes.Yes | Yes.Content hashes | No.By name and size | No.Paid editions |
| Shows what changed since the last scan | Yes.Changes view | Partly.Saves and reopens scans | Partly.CSV export and import | No.Paid editions |
| Says what is safe to clear | Yes.Insights view | Partly.Cleanup tools you run | No.Not described | No.Not listed |
| Export | Yes.CSV, TSV, picture | Yes.CSV, JSON | Yes.CSV | Partly.PDF only |
Checked on 11 November 2026 against windirstat.net, diskanalyzer.com (the guide and the What's new page) and jam-software.com (the TreeSize Free page and the edition comparison). Products change; if something here is out of date, open an issue and it gets fixed.
What to look for
What matters when you pick one
Scan speed. On an NTFS drive the fast tools read the master file table instead of opening every folder, which turns minutes into seconds. It needs administrator rights.
How the result reads. A treemap shows the whole drive at once; a tree shows one folder at a time. Maps with names on the boxes can be read without a list beside them.
What happens next. Finding the big folders is the start. Duplicate search, a comparison with an earlier scan and a list of what is safe to clear decide how quickly you get the space back.
The license. Check it before using a tool at work: two of these four are free only for private use.
How this page is kept
Written by the maker of one of them
This page is on SpaceSharp's website, so read it with that in mind. To keep it fair, every statement about another product comes from that product's own website or documentation, and where those pages do not say, the table says so and makes no guess.
We have not benchmarked the four against each other and make no claim about which scans fastest.
Each comparison page has a section on where the other program is the better choice. If a newer version has changed something, open an issue and it gets corrected.
Questions
Choosing a disk space analyzer
What is the best free disk space analyzer for Windows?
It depends on how you like to read a drive. SpaceSharp and WinDirStat are both free and open source with treemaps; SpaceSharp writes names on the boxes and compares scans over time, WinDirStat adds sunburst and flame graphs. WizTree is free for personal use and known for speed. TreeSize Free suits people who prefer a folder tree.
Which disk space analyzers are open source?
Of these four, SpaceSharp (MIT license) and WinDirStat (GPL). WizTree and TreeSize are closed source.
Which ones can I use at work for free?
SpaceSharp and WinDirStat. WizTree asks commercial users to buy a Supporter Code or license, and TreeSize Free is for private, non-commercial use.
Why are some scans so much faster than others?
On NTFS drives a tool can read the master file table, a single index of every file, instead of opening each folder in turn. SpaceSharp, WinDirStat and WizTree all do this when run as administrator.
Which ones find duplicate files?
SpaceSharp and WinDirStat compare file contents. WizTree matches by name and size, optionally date, without comparing contents. TreeSize has duplicate search in its paid editions, not in TreeSize Free.
Is SpaceSharp safe to use?
Every download is code-signed, the source is public, and the app has no telemetry, account or ads. Deleting goes through the Windows Recycle Bin, so a mistake can be restored.
More comparisons
Looking at another one?
Try it on your own drive.
SpaceSharp is free and open source. Scan a drive and judge it for yourself.
v2.9.0 · Windows 10 and 11 · MIT · code-signed · no telemetry