TreeSize Free

GrandPerspective

GrandPerspective is a free macOS utility that scans a folder or volume and displays disk usage as a treemap, where each file is drawn as a rectangle sized proportionally to how much space it consumes. This makes it fast to spot the largest files and folders visually rather than digging through nested Finder windows. Released under the GNU General Public License, GrandPerspective supports multiple color-mapping schemes (by file type, size, or modification date), filtering and search, and can compare or combine multiple scans. It is distributed for free from SourceForge, with an optional paid copy on the Mac App Store for users who prefer automatic updates and app-review verification.

WinDirStat

WinDirStat is a free, open-source disk usage analyzer for Microsoft Windows that scans drives and folders and shows how disk space is distributed across the file system. It uses multithreaded scanning with direct NTFS support and presents results as sortable lists, extension statistics, a Largest Files view, and an interactive treemap that makes it easy to visually spot which folders and file types are consuming the most space. Beyond basic scanning, WinDirStat can detect duplicate files by content, inspect file permissions, and analyze storage tiers, and it supports file operations like opening, moving, or deleting items directly from the results view. It also offers dark mode, Windows Explorer integration, file-system change monitoring, and scan export, and is distributed under the GNU General Public License version 2 (GPLv2) with source code hosted on GitHub.

WizTree

WizTree is a free disk space analyzer for Windows built by Antibody Software that scans entire hard drives in seconds by reading the NTFS Master File Table directly instead of walking the file system folder by folder. It renders results as an interactive treemap so users can visually spot the largest files and folders on a drive at a glance, then delete or move them without digging through Explorer. Beyond the core treemap view, WizTree includes a duplicate file finder, CSV export for reporting, and support for non-NTFS and network drives via a slower standard scan. The free version is for personal use only; commercial users need a Supporter license priced by organization size, or an Enterprise license for unlimited use across a company.