TreeSize Free vs WinDirStat: Which Disk Space Tool I Actually Keep Installed

What do you actually do when Windows tells you the drive is full and you have no idea why? You install a disk space analyzer, obviously. The interesting part is what happens six months later, when you look at your installed programs and realize you only ever open one of them. In my case, two candidates went head to head: TreeSize Free and WinDirStat. I have used both, and one of them is still on my machine.

Let me be upfront: this is not a symmetric comparison. It never was. WinDirStat has a decade of goodwill behind it, it is open source, and it looks exactly like a program designed in 2005 because it was. That is not automatically a bad thing. But time passes, drives get bigger, and impatience gets worse.

How I judge a disk analyzer

I run roughly the same test on every one of these tools. I point it at a full C: drive with a few hundred thousand files, and I watch three things: how fast it finishes, whether the treemap makes the file hogs obvious without hunting, and whether I can act on a file without bouncing into File Explorer.

That last one separates a toy from a tool. Finding the 40GB culprit is half the job. Removing it (or renaming it, or copying its path into a backup script) is the other half.

Where TreeSize Free stands

TreeSize Free is the more conservative of the two. It presents a hierarchical tree of folders sorted by size, and you drill down from the top. The column view is excellent for the obvious question: which folder is eating my drive? It can expand the whole tree, it reads the Windows folder structure competently, and it feels like a proper Windows utility rather than a project.

Its treemap view is there, but it always felt secondary to me. I used TreeSize the way I use a file manager with a size column turned on. Which is fine. Fine is not the same as fast.

Speed is the sore point. The traditional approach crawls folder by folder, and on a big drive with lots of small files you can watch it grind. Not torture, but enough that I started launching scans and walking away. That habit alone tells you something.

Where WinDirStat stands, and why I stopped reaching for it

WinDirStat is the classic of the genre. Pac-Man style blocks, extension-colour legend, blunt but effective. If you learned disk analysis on it, it shaped how you read a treemap.

My problem is that it has not moved meaningfully with the times. The interface is dated, the scan speed reflects the folder-crawling method, and on drives with hundreds of thousands of files the wait is real. It still works. It just stopped being the first thing I open.

And then there is the file management gap. Once a WinDirStat scan finishes, finding the file is a read-only experience, and dealing with it sends me back to Explorer. That friction compounds.

The tool I actually keep

WizTree is the one that stayed. I did not plan on switching, exactly. I tried it once on a full drive out of curiosity, and the speed made both of the older tools feel dated in a single session.

The mechanism explains it. WizTree reads the NTFS Master File Table directly instead of crawling the file system folder by folder (the same basic approach that makes the Everything search app so fast). The MFT already holds the metadata about every file and folder on an NTFS volume, so reading it wholesale beats walking the tree. In one test I read about, a C: drive with roughly 300,000 files scanned in under a second and a half. I cannot promise you the same number on your hardware, but the order of magnitude matches what I saw. Scans that used to involve a coffee no longer do.

WizTree is not NTFS-only. It handles exFAT and FAT32, network drives, and MTP/PTP connected devices such as phones and cameras. That matters more than it sounds, since half my “where did the space go” problems live on a phone or an external drive.

The treemap deserves a mention because it is the same idea as WinDirStat’s, executed more cleanly. Files and folders become colour-coded blocks scaled to their real footprint, so the largest consumers physically dominate the screen. You are not reading percentages. You are looking at which rectangle is swallowing your SSD.

Then the part that sealed it: file management without leaving the window. Right-click any block and I can rename, copy the path, or delete the file on the spot. I once spotted a forgotten video file in the treemap and dealt with it in two clicks. No Explorer detour.

The caveat nobody should skip

A tool that deletes files quickly is a tool that deletes the wrong files quickly. A large block in WizTree does not mean it is safe to remove. System files, application data, and caches that Windows and your apps actively need all show up as perfectly deletable-looking blocks. I check twice before deleting anything I did not personally create, and I strongly suggest you do the same. Speed here is a convenience and a hazard in equal measure.

The honest verdict, such as it is

If you want one installer and no deliberation: WizTree. The MFT-based scanning, the readable treemap, the built-in file operations, and the breadth of supported drives and devices put it ahead. It is free for personal use, with a paid business licence for commercial environments, which is a reasonable arrangement for a tool this useful.

TreeSize Free remains a perfectly decent fallback if you want a pure tree view and nothing else. WinDirStat I would now recommend only to someone who already knows it and does not mind the wait. Neither is bad. They just got outrun.

My drive is still mostly full, by the way. But now I know exactly what is eating it, and I no longer guess.