When Windows Settings shows your drive is full but does not reveal exactly why, a disk space analyzer is the answer. We tested five popular tools to help you choose.

Test Environment

Windows 11 23H2, Ryzen 7 7700X, 32 GB DDR5, Samsung 990 Pro 2 TB NVMe SSD with 1.4 TB of data (~2.8 million files). Each tool was run three times; we recorded the average scan time.

WizTree

Developer: Antibody Software · Price: Free (personal), $15 (commercial) · Scan time: 4.2 seconds

WizTree reads the NTFS Master File Table (MFT) directly instead of scanning files individually through the Windows API. This makes it dramatically faster — seconds rather than minutes.

Interface: Sortable directory tree on top, treemap visualization on bottom, plus a file view tab that lists every file sorted by size.

Strengths: Unmatched speed, file name search with wildcards, CSV export, portable version, under 10 MB installed.

Considerations: Requires admin privileges for MFT scanning. MFT scanning only works on NTFS volumes (falls back to standard scanning for others). Treemap less polished than WinDirStat.

Our take: Clear winner for speed and efficiency. The file search feature adds genuine utility beyond basic visualization.

WinDirStat

Developer: Open source · Price: Free · Scan time: 6 min 38 sec

The classic Windows disk analyzer since 2003. Uses file-by-file scanning, making it significantly slower than MFT-based tools.

Strengths: Fully free and open source, color-coded treemap by file type, file extension statistics view, well-documented.

Considerations: Nearly 100x slower than WizTree in our test, no file search, interface looks dated, can be unresponsive during scans.

Our take: Solid free option with unique file-type visualization. Best for users who prioritize open-source software.

TreeSize Free

Developer: JAM Software · Price: Free / Pro $24.95 · Scan time: 3 min 12 sec

Explorer-like tree interface with size bars. Integrates into the Windows context menu.

Strengths: Familiar interface, Explorer context menu integration, touch-friendly, Professional version adds search and export.

Considerations: Free version lacks search and treemap, slower than WizTree.

Our take: Best for users who prefer a traditional file-manager interface.

SpaceSniffer

Developer: Uderzo Software · Price: Free · Scan time: 4 min 47 sec

Portable application with a zoomable, interactive treemap and powerful filtering.

Strengths: No installation required, zoomable treemap, filtering by type/age/size, under 3 MB.

Considerations: Can feel cluttered on drives with millions of files, no file list view.

Our take: Best for portable use — keep on a USB drive for diagnostics on client machines.

Windows File Explorer (Built-in)

Developer: Microsoft · Price: Included

Not a dedicated analyzer, but can sort by size and the Storage Settings page provides category-based analysis.

Our take: Start here, move to a dedicated tool when you need more detail.

Speed Comparison

WizTree's MFT-based scanning is roughly 45–95x faster than standard file enumeration. The difference is even larger on HDDs.

Our Recommendation

For most users, WizTree is the best overall choice — fast, capable, and free for personal use. For open-source preference, WinDirStat remains excellent. For portable diagnostics, keep SpaceSniffer on USB.

For a step-by-step guide using these tools, see our complete Windows disk cleanup guide.