SpaceFree vs WizTree vs TreeSize vs WinDirStat: which Windows storage tool should you use?

Four tools, two different jobs

WizTree, TreeSize and WinDirStat all do the same core job: scan a drive and show you which folders are largest, usually with a treemap visualization. SpaceFree does a narrower, different job: it identifies specific developer storage, such as WSL2 virtual disks, Docker Desktop images, package caches and AI coding assistant caches, and tells you which parts are actually safe to remove. Worth understanding the difference before picking one, since they solve different problems.

WizTree: built for speed

WizTree's defining feature is how it scans: instead of walking through folders one at a time, it reads the NTFS Master File Table (MFT) directly, which is why it can scan an entire large drive in seconds where a traditional folder walk takes minutes. It shows a folder tree plus a treemap view, and is free for personal use, with a separate Pro edition licensed for commercial use. What it does not do is distinguish a WSL2 virtual disk or a Docker image from any other large file, it is a size number attached to a path, nothing more.

TreeSize: built for ongoing monitoring

TreeSize, from JAM Software, is aimed less at a one-off cleanup and more at tracking storage over time. The free edition does a standard folder-by-folder scan; the paid Professional and Business editions add scheduled scans, exportable reports, duplicate file search, and scanning across network drives, which is why it is common in IT departments monitoring storage across a fleet of machines rather than on a single developer's laptop. Like WizTree, it has no concept of what a WSL2 or Docker file actually is, only that a given path is a given size.

WinDirStat: free and simple

WinDirStat is completely free and open source under the GPL license, with no paid tier at all. It uses a folder-by-folder scan, which is slower on a large modern drive than the MFT-reading approach WizTree uses, and it was one of the tools that popularized the treemap visualization style other disk analyzers now also use. Development has been slow in recent years compared to actively maintained commercial tools, but it remains a solid, no-cost option for a single quick look at where space is going.

Where SpaceFree does something different

WizTree, TreeSize and WinDirStat all answer the same question: where is my space going, by folder. SpaceFree answers a different question: which specific developer tool put this data here, and can it actually be removed safely. That distinction matters in practice. A WSL2 .vhdx file does not shrink on its own even after files are deleted inside it, so a generic size scanner just reports a large, seemingly permanent file. Docker Desktop's own reported usage can diverge from what is actually sitting on disk. Package caches from npm, pip and NuGet are meant to be deleted, they rebuild automatically, but a generic scanner shows them identically to files that would be lost forever if removed. AI coding assistant caches (Claude Code, Codex CLI, Cursor, Windsurf and others) are new enough that none of the other three tools have a category for them at all yet.

• Safe to delete — data any tool can regenerate without you doing anything, such as most caches.
• Rebuildable — data that comes back automatically the next time it is needed, such as package caches that redownload on the next install.
• Not cleanable — data SpaceFree cannot confirm is safe, so it is left alone rather than guessed at.

Developer storage feature checklist

This is not a general "which tool is better" scorecard, since WizTree, TreeSize and WinDirStat are all solid, mature tools for what they do. It is specifically about developer storage awareness: whether a tool understands what created a given piece of data, or only reports its size.

Which one should you actually use

These tools are not mutually exclusive. It is reasonable to keep WizTree or WinDirStat around for a general look at any drive, and use SpaceFree specifically for the developer storage question none of them answer. Download SpaceFree.