SpaceMonger

Drive full, and no idea why? Windows tells you that space is running out, but not where it went. Explorer shows no folder sizes, so you click through folder after folder. SpaceMonger scans the drive in seconds and draws every folder and file as a box, sized by the space it takes, with name, size and date written on it. The big boxes are what fills your drive: you see it at a glance, without opening a single folder.

What people use it for:

• Free up a full drive. Find the forgotten video, the old ISO image, the Outlook archive or the download folder nobody cleaned up, and move it to the Recycle Bin. Temporary files, caches and the Recycle Bin go in one click.
• Decide before buying. See whether you really need a bigger SSD, or just a cleanup, before you migrate a PC.
• Help desk. Look at a colleague's drive from your own desk over the admin share (\\PC01\c$), without installing anything on their PC.
• File servers. See which project, department or backup fills a share.
• IT inventory. Collect a CSV report from every PC on a share, run without a window from a logon script or a scheduled task.

Download

Windows	File
64-bit (most PCs)	SpaceMonger-x64.exe
ARM64 (Snapdragon, Surface Pro X)	SpaceMonger-arm64.exe
32-bit (legacy)	SpaceMonger-x86.exe

One signed exe, no installer: save it anywhere and start it. How to verify a download.

Features

All screenshots show a demo folder with placeholder files.

See where the space is

Every box carries its name, size and date as long as it fits; folders show their total in the title bar. Double-click a folder to zoom in, the path bar above the map takes you back up.

• Scan a drive, a folder (Open > Folder..., or drop it on the window) or a network share.
• Zoom with a double-click, the mouse wheel or the keyboard; the path bar shows where you are, and each part of it is a link.
• Tooltips with full path, size, share of the drive, contents and date.
• On a whole drive, the free space is a block of its own, and Windows folders (Windows, Program Files, ...) are shown muted or can be hidden, so the eye goes to what you can change.

Find things

Type into the search field (Ctrl+F): everything that does not match is washed out, and the count of matches appears next to it.

See what kind of files they are

By file type colours videos, pictures, music, documents, archives and disk images, and programs, with a legend above the map. Dark mode follows Windows or can be set in the settings.

Free up space

Clean Up removes temporary files, browser caches and the Recycle Bin in one click. Below, your biggest files are listed with a tip for each; tick what you no longer need and move it to the Recycle Bin together.

• Nothing is ever selected for you, and deleting always goes to the Recycle Bin.
• Show in Explorer, Properties and Delete also work on any box in the map (right-click).

For administrators

• Command line scans and headless CSV reports, see Command line.
• Report button: the scan as an HTML page with the map (see HTML report), saved to Documents\SpaceMonger and opened in the browser.
• CSV export of the biggest folders and files from the window (the Report button, Ctrl+E; Ctrl+Shift+E asks where to save and offers CSV).
• Run as administrator restarts elevated with the same path, for folders the user cannot read.

Looks like Windows today

• Fluent icons, light and dark mode, sharp text at any DPI and on mixed-DPI monitors.
• English, German and French, following the Windows display language.
• Colours by depth (the classic look), muted, Windows colours or by file type.

Under the hood

• Multithreaded scanner; the map builds live while the scan runs.
• Unicode names and long paths end to end; junctions, symlinks, sparse files and cloud placeholders (OneDrive and others) are accounted for correctly.
• Honest numbers: a failed scan is an error, and space that could not be read shows up as Unavailable (estimate) instead of disappearing.
• Settings live in HKCU\Software\65\SpaceMonger; the program writes no other files than the reports and exports you ask for. No telemetry, no update checks.

Known limitation: hard links are counted once per link. Details in README.TXT.

Why this fork

SpaceMonger has done one thing better than anything else since 1998: the nested, labelled treemap. Pie charts and sorted lists show one level at a time; SpaceMonger shows all of them at once, and the big boxes are where the work is. That idea has aged well. The program around it had not: no signature, no way to run it unattended, no answer for network shares, and a look from Windows 98.

This fork keeps the idea and closes the gaps that stop it from being used in a company:

Need in a company	What this fork does
Software from the internet must be trustworthy	Authenticode-signed (Certum), SHA256SUMS, Sigstore build provenance, CodeQL and OpenSSF Scorecard
Nothing to install, nothing to clean up	One standalone exe for x64, ARM64 and x86; static MFC and runtime, no installer, no services, no telemetry or update checks
Help desk looks at a user's PC	Scan a remote PC over its admin share: SpaceMonger.exe \\PC01\c$
File servers and shares	Scan any folder or UNC path, drag and drop, Run as administrator for folders the user cannot read
Inventory across many PCs	Headless /report: no window, a CSV per computer to a share, exit codes for scripts
Numbers that hold up	Failed scans are errors, unreadable space is shown as Unavailable (estimate) instead of disappearing, junctions, symlinks and cloud placeholders are not counted twice
Users who are not technicians	Windows look, dark mode, German, English and French, system folders muted, Clean Up for safe space (temp, caches, Recycle Bin), everything else goes to the Recycle Bin

The original treemap, its colours and its speed stay as they were.

Command line

SpaceMonger.exe [path] [/report <file or folder>] [/html <file or folder>] [/top N] [/hide-system]
SpaceMonger.exe /register | /unregister

Example
SpaceMonger.exe D:\	opens the window and scans D: right away
SpaceMonger.exe \\PC01\c$	an admin scans a remote PC over its admin share
SpaceMonger.exe /report \\srv\reports\	no window: scans the Windows drive, writes \\srv\reports\<COMPUTER>_<yyyy-mm-dd>.csv and exits
SpaceMonger.exe \\PC01\c$ /report pc01.csv /top 50 /hide-system	remote report with the 50 biggest folders and files, without system content
SpaceMonger.exe /html "%OneDrive%\Disk report\"	no window: writes the map of the Windows drive as an HTML page into the user's OneDrive
SpaceMonger.exe /register	lets Show in Explorer in the HTML page open Explorer (current user only); /unregister removes it

Exit codes: 0 done, 1 invalid arguments (/? prints the usage to the calling console), 2 scan failed, 3 report not written, 4 link refused or registration failed.

The report starts with drive size, used, free and not readable space, then lists the largest folders and files. It is UTF-8 with the list separator of the user's locale, so Excel opens it in columns. An excerpt (/top 8):

Computer	Kind	Path	Size (GB)	Share (%)	Files	Modified	System
PC-0142	Folder size	C:\FileServer\	18.79		548
PC-0142	Folder	C:\FileServer\Projects\	4.49	23.9	116	2026-10-24	no
PC-0142	Folder	C:\FileServer\Users\	4.29	22.9	124	2026-10-24	no
PC-0142	Folder	C:\FileServer\Backups\	3.83	20.4	9	2026-10-24	no
PC-0142	File	C:\FileServer\Backups\Server\SRV01_full_01.vhdx	1.10	5.8		2026-06-19	no
PC-0142	File	C:\FileServer\Users\Chris\Outlook\archive_02.pst	0.87	4.7		2025-06-30	no

The full file also has the size in bytes and the scan date.

HTML report

/html, the Report button in the window (Ctrl+E) write one self-contained page with the same map as the window: hover for details, double-click a folder to zoom in or a file to show it in Explorer, the biggest folders and files below. It needs no network, sends nothing anywhere and opens in any browser, so it can be put into the user's OneDrive or sent by mail. A whole drive is a few hundred KB.

Show in Explorer uses spacemonger: links, which work once SpaceMonger.exe /register has run for the user. The Report button does that by itself the first time it writes a page (current user only, no administrator needed); /register is for pages made with /html on a machine where nobody has used the window yet. Since any web page can open such a link, SpaceMonger accepts only plain local paths (C:\...): no shares, no device paths, no ... A link only selects the item in Explorer; nothing is ever deleted or changed through it.

Rolling it out in a company

SpaceMonger is one signed exe without an installer, services or network access, so rolling it out means copying a file and running it with the right arguments. Three ways to use it, from the one that needs the least from IT to the one that needs the most:

	Who looks at the data	What IT handles
Report for every user (recommended)	each user, their own drive	a script, no data
Help desk	the technician, on request	one remote drive at a time
Inventory	IT, all PCs	CSV files with paths, on a share

1. Put the exe on the PCs

Copy SpaceMonger-x64.exe (or the ARM64 build) to C:\Program Files\SpaceMonger\SpaceMonger.exe, with Intune (Win32 app), Configuration Manager, a GPO file copy or your own tool. Check the signature first, see verifying a download. Users can start it from a shortcut; settings go to HKCU\Software\65\SpaceMonger, nothing has to be configured.

2. A report for every user, without IT touching the data

Every PC writes the map of its own drive as an HTML report into the user's OneDrive, only when the drive is getting full. The user opens it in the browser, sees what takes the space and jumps to it in Explorer. File names never leave the user's account: IT sees only whether the script ran.

flowchart LR
  A["Intune remediation<br>or scheduled task<br>(user context, weekly)"] --> B{"Drive more than<br>85 % full and no<br>report this week?"}
  B -- no --> Z["nothing happens"]
  B -- yes --> C["SpaceMonger.exe /html<br>scans C:, writes<br>PC_date.html"]
  C --> D["OneDrive\Disk report<br>(only the user)"]
  D --> E["User opens it: map,<br>biggest files,<br>Show in Explorer"]

Loading

With Intune (Devices > Scripts and remediations > Remediations): create a script package with the two scripts below, set Run this script using the logged-on credentials to Yes and the schedule to weekly. Intune then reports per device only whether the drive was over the limit and whether the report was written.

Detection script: asks for a report when the drive is more than 85 % full and none was written in the last 7 days.

$drive = Get-PSDrive -Name $env:SystemDrive.TrimEnd(':')
$usedPercent = 100 * $drive.Used / ($drive.Used + $drive.Free)
$folder = if ($env:OneDrive) { Join-Path $env:OneDrive 'Disk report' }
          else { Join-Path ([Environment]::GetFolderPath('MyDocuments')) 'SpaceMonger' }
$recent = Get-ChildItem $folder -Filter *.html -ErrorAction SilentlyContinue |
          Where-Object LastWriteTime -gt (Get-Date).AddDays(-7)
if ($usedPercent -gt 85 -and -not $recent) { exit 1 }   # run the remediation
exit 0

Remediation script: sets up Show in Explorer for the user and writes the report (<COMPUTER>_<yyyy-mm-dd>.html).

$exe = "$env:ProgramFiles\SpaceMonger\SpaceMonger.exe"
$folder = if ($env:OneDrive) { Join-Path $env:OneDrive 'Disk report' }
          else { Join-Path ([Environment]::GetFolderPath('MyDocuments')) 'SpaceMonger' }
New-Item -ItemType Directory -Force $folder | Out-Null
Start-Process $exe -ArgumentList '/register' -Wait
$scan = Start-Process $exe -ArgumentList '/html', "`"$folder`"" -Wait -PassThru
exit $scan.ExitCode   # 0 = written, see "Command line" for the others

To show the report right away instead of leaving it in the folder, add Get-ChildItem $folder -Filter *.html | Sort-Object LastWriteTime | Select-Object -Last 1 | Invoke-Item before the exit.

Without Intune: a GPO scheduled task (*User Configuration > Preferences

Control Panel Settings > Scheduled Tasks*, Run in logged-on user's security context) that starts `powershell.exe -ExecutionPolicy Bypass -File

<script>` weekly with both parts in one script: the check, then the report. Tell users once where the report appears, for example in the intranet: *If your drive is getting full, you'll find a map of it in OneDrive under "Disk report".* ### 3. Help desk `SpaceMonger.exe \\PC01\c$` on an admin workstation shows a remote drive over its admin share, without installing anything on that PC. *Report* in the toolbar writes the HTML page of it, to attach to the ticket. ### 4. Inventory across all PCs For an overview of where space goes across the fleet, run the CSV report as SYSTEM (scheduled task or deployment tool) and collect it on a share: ```text "C:\Program Files\SpaceMonger\SpaceMonger.exe" /report \\srv\reports$\ /top 50 ``` Each PC writes `_.csv` (biggest folders and files, drive size, used, free). As SYSTEM it can read every folder; as a user, other users' folders show up as *Not readable*. Give the computer accounts only *create files* on the share, no read. The CSV contains paths and file names, which are personal data: agree on it with data protection (and, in Germany, the works council) first, or prefer the per-user report above. ### Removing it Delete the exe. Per user, `SpaceMonger.exe /unregister` removes the `spacemonger:` link, and `HKCU\Software\65\SpaceMonger` holds the settings. Nothing else is left behind. ## Documentation | Topic | | |---|---| | [Architecture and current state](docs/ARCHITECTURE.md) | components, scan flow, dependencies, pipeline (with diagrams) | | [Build and test](BUILDING.md) | Visual Studio 2022, CMake presets for x86/x64/ARM64 | | [Releasing](docs/RELEASING.md) | signed release runbook, one-time setup, troubleshooting | | [User guide](README.TXT) | usage, disk accounting, partial scans, version history | | [Backlog and decisions](BACKLOG.md) | priorities, distribution and UI constraints | | [Changelog](CHANGELOG.md) | release notes source | | [Contributing](CONTRIBUTING.md) · [Code of Conduct](CODE_OF_CONDUCT.md) · [Security](SECURITY.md) | | Historical implementation records: [treemap design](docs/superpowers/specs/2026-08-15-treemap-layout-engine-design.md) / [plan](docs/superpowers/plans/2026-08-15-treemap-layout-engine.md), [live-scan design](docs/superpowers/specs/2026-08-15-live-progressive-treemap-scan-design.md) / [plan](docs/superpowers/plans/2026-08-15-live-progressive-treemap-scan.md). They describe the original work; implementation-status notes record later decisions. ## Support the project SpaceMonger is free and funded by donations: [GitHub Sponsors](https://github.com/sponsors/JRpersonal) · [Ko-fi](https://ko-fi.com/streborn) · [PayPal](https://paypal.me/JR31337). ## Open source SpaceMonger is free software under the [MIT License](LICENSE.txt). - **Original author:** Sean Werkema, SpaceMonger 1.0 to 1.4.0 (1998–2000), source published as [seanofw/spacemonger1](https://github.com/seanofw/spacemonger1). - **Modernization:** Johnny J. Andersen, releases 1.4.1 to 1.4.4 at [Daduck/spacemonger](https://github.com/Daduck/spacemonger). - **This fork:** Jens Roggenfelder, signed releases, production CI/CD and the changes for use in companies. Changes that are not fork-specific are offered upstream. The executable statically links MFC and the MSVC runtime and has no other dependencies. Licenses of everything involved are listed in [THIRD-PARTY-NOTICES.md](THIRD-PARTY-NOTICES.md).