WizTree, TreeSize Free, and WinDirStat are strong free options for finding what is using space on a Windows PC. WizTree’s publisher describes direct Master File Table scanning for NTFS drives; TreeSize Free offers a familiar folder view, treemap, and PDF reports for personal, non-commercial desktop use; and WinDirStat is an open-source option with sortable file lists and several visualizations. These are documented feature differences, not results of a head-to-head speed test.
If you only need basic cleanup, start with Windows’ built-in Storage settings and Cleanup recommendations. An analyzer can show what is large, but it cannot determine whether a file is safe to delete.
Which free Windows disk space analyzer should you choose?
| App | Good fit for | Notable documented features | Free-use limits |
|---|---|---|---|
| WizTree | Readers who want to inspect an NTFS drive using the publisher’s stated direct-scan method and locate large files. | Tree view, treemap, file search, CSV import and export, and duplicate finding. | Free version is for personal use; commercial options are paid. |
| TreeSize Free | Readers who prefer a conventional folder structure and want a visual allocation map or PDF report. | One-click visualization down to file level, treemap, and PDF reports. | Personal, non-commercial desktop use only; not for Windows Server. Paid editions are separate. |
| WinDirStat | Readers who prefer open-source software and multiple ways to explore file usage. | Sortable file lists, file-type statistics, interactive treemap and other graphs, large- and duplicate-file discovery, reports, and cleanup operations. | GPL v3 or later; the project says it is free for personal and commercial use. |
For Windows version support, WinDirStat’s project documentation lists Windows 7, 8, 8.1, 10, and 11 among tested versions, as well as several Windows Server releases. That does not make TreeSize Free suitable for servers: its publisher explicitly excludes Windows Server use. Check each publisher’s current requirements before installing, since support and licensing can change.
What each app offers
WizTree: direct NTFS scanning and file discovery
WizTree’s publisher says it reads the Master File Table directly when scanning NTFS drives. It also documents scans of non-NTFS and network drives. That is a description of its scan method—not an independent comparison proving it is faster than the other apps on your PC. Its feature list includes a folder tree, treemap, file search, CSV import and export, and duplicate finding.
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The free version is for personal use. If you are evaluating an analyzer for a work device or commercial setting, check the publisher’s licensing terms rather than assuming the personal-use version covers it.
TreeSize Free: folders, treemap, and PDF reports
TreeSize Free is a fit if you want to follow a recognizable folder hierarchy and also see a visual representation of space allocation. Its publisher lists file-level visualization, a treemap, and PDF reports. The free edition is for personal, non-commercial use on desktop systems and is not usable on Windows Servers; do not assume features from paid TreeSize editions are included in Free.
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WinDirStat: open source and multiple views
WinDirStat combines sortable file details and file-type statistics with an interactive treemap and other graphs. The project also documents tools for finding large and duplicate files, generating reports, and performing cleanup operations. It is licensed under GPL v3 or later and described by the project as free for personal and commercial use.
Because WinDirStat exposes file operations, inspect the selected item and its location before using a cleanup action. A visualization tells you where space is occupied; it does not establish that deletion is safe.
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One-click scans. No signup required.
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SpaceSniffer: verify before relying on it
SpaceSniffer appeared in search results as a free, portable analyzer with a treemap-style interface, but the available evidence here does not establish a current version or a Windows compatibility list from an original developer source. For a tool whose current support and official download source matter, prefer one of the better-documented options above unless you can verify those details directly.
How to choose between them
- Choose by view: decide whether you want a folder tree and sortable list, file-type breakdown, treemap, or report. WinDirStat documents several types of views; TreeSize Free specifically lists a treemap and PDF reports.
- Choose by scan method, not an unverified speed ranking: WizTree’s publisher describes direct Master File Table reading on NTFS. There is no same-machine comparative benchmark here to establish a universal fastest app.
- Match the license to your use: WizTree Free is for personal use, and TreeSize Free is for personal, non-commercial desktop use. WinDirStat’s project describes its GPL-licensed software as free for personal and commercial use.
- Check Windows support and download route: review the current publisher or project documentation, especially for older Windows releases, server systems, or managed work devices.
How to analyze disk use without deleting the wrong thing
- Check available space first. Open File Explorer and select This PC to see available drive space, or review Windows Settings > System > Storage. Microsoft notes that low storage can cause slower performance or trouble installing Windows updates.
- Scan the drive and inspect the largest items. Use the app’s folder list or treemap to find unusually large folders and files. If you use duplicate finding, treat it as a separate check: two matching files may still serve different purposes or be stored in different locations for a reason.
- Confirm what a file is before removing it. Open its location and identify its purpose. Do not delete Windows system folders or unfamiliar application data just because an analyzer reports a large size.
- Use Windows cleanup controls for routine cleanup. In Settings > System > Storage, review Storage Sense and Cleanup recommendations. Microsoft says these built-in tools show categories such as temporary files, large or unused files, cloud-synced files, and unused apps, with estimated savings before you select cleanup. Deleting a previous Windows installation can remove the option to return to the prior version.
- Move files you want to keep if you need space on the PC. Microsoft lists external storage such as USB drives and SD cards as options. This is optional: an external drive is not required to analyze disk usage.
Download from the official source
Use the publisher or project’s own download page rather than a third-party download site. WinDirStat specifically warns about imitation download sites that may provide outdated or modified files and points users to its Store, package manager, official releases, or project site. Confirm that the download route and license still match your needs before installing.
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