Space Report

Disk usage tools tell you what is big. This one tells you what it is, and whether you can delete it.

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Every disk analyser gives you the same thing: a treemap full of enormous files with inscrutable names. hiberfil.sys. System Volume Information. WinSxS. A 6 GB .ost. Which of those can you delete? The tool never says, so you either leave it all alone or you google each one in turn.

Space Report annotates every large file with a plain-English description, a verdict, and the correct way to reclaim it:

Verdict	Meaning
SAFE	Delete freely — rubbish, or it regenerates itself
TOOL	Reclaimable, but use the command shown, not Explorer
REVIEW	Your data or your software — only you can decide
KEEP	Something installed needs this; deleting degrades or breaks it
NEVER	Deleting breaks Windows or loses data permanently

Around 100 rules cover Windows internals, dev toolchains, games, creative apps, cloud sync, browsers and VM disks. Anything unrecognised is reported as UNKNOWN rather than guessed at.

Two ways to use it

The app — pick a drive, scan, tick, delete.

Filter to everything marked SAFE and take the lot in one click:

Progress is a real percentage — bytes scanned against the drive's used space — not a spinner that tells you nothing:

And the part no big-files tool shows you: the Disk Cleanup categories, which are thousands of small files each and so can never appear in a size-ranked list. Several of these can only be measured with administrator rights — see Normal mode and administrator mode:

Normal mode and administrator mode

The app runs without administrator rights by default, deliberately — a double-click should never be able to quietly remove protected files. Everything that matters works in that mode.

	Normal	As administrator
Finds every file on the drive	yes	yes
Classification, verdicts, guidance	yes	yes
Selecting and deleting files	yes	yes
Recycle Bin size and access	yes	yes
Measuring protected system areas	no	yes

The single difference is the System cleanup section. Windows blocks ordinary programs from reading several of those folders, so without elevation they report needs admin instead of a size:

• Delivery Optimization cache — update chunks shared with other PCs on your LAN
• Windows Search index — Windows.edb, which occasionally runs away to tens of GB
• Defender scan history
• Kernel telemetry dumps — LiveKernelReports, which grows when a driver keeps resetting
• The system temp folder, and the prefetch folder

This is not a small difference. On the machine these screenshots came from, normal mode could measure 458 MB of system cleanup areas; the same scan as administrator found 19.1 GB — 8.3 GB of it Delivery Optimization and 7 GB of kernel telemetry dumps, neither of which was visible at all beforehand.

The app offers elevation when it starts, and there is a Run as admin button in the header and beside the locked rows. Choosing it restarts the app and asks Windows for permission, so you will need to run the scan again — which is why it asks up front rather than after you have waited for a scan.

The script — same engine, no GUI.

# What is using the drive?
.\Get-SpaceReport.ps1 -Path C:\ -MinSizeMB 1000

# Every file over 5 GB, plus an HTML report
.\Get-SpaceReport.ps1 -MinSizeMB 5000 -Top 0 -Html

# Pick files to delete from a tick-box list
.\Get-SpaceReport.ps1 -MinSizeMB 500 -Clean

Deleting is deliberately hard to get wrong

Files are only removable when a plain file delete is genuinely the right move. Three categories are held back on purpose:

• BLOCKED — verdict NEVER, plus a path-based list that protects .pst, .lrcat, virtual disks, game saves, pagefile.sys and hiberfil.sys regardless of how they were classified
• use app — belongs to a game, Store app or SDK. Removing one file out of an install corrupts it; the launcher just re-downloads it
• use command — has a proper command, or is locked while Windows runs

That second check keys off the path, not the classification, and it exists because testing found a real failure: a .pst sitting under AppData\Local\Temp was classified "your temp folder, SAFE" because a broad location rule matched before the file-type rule. Location was overriding identity. Rails that depend on classification being right are not rails.

Everything else:

• Files go to the Recycle Bin by default (-Permanent to bypass)
• A typed DELETE confirmation in the script; a modal in the app
• Refusals are printed loudly, never dropped silently
• The app holds no knowledge of what is safe to delete — it shells the script for both scanning and deleting, so there is one source of truth and the two cannot drift apart
• Folders are never deletable from the tool. They are shown for context only

Install

App — download SpaceReport.exe from Releases and run it. One file, nothing to unzip, no .NET install needed. It unpacks its own working files to %LOCALAPPDATA%\SpaceReport on first run.

Windows will show "Windows protected your PC" on first run because the executable is unsigned. More info → Run anyway. Code signing needs a paid certificate.

Optional arguments, if you want a shortcut that goes straight to a scan:

SpaceReport.exe --scan C:\ --min 500 --view system

Script — PowerShell 7 (pwsh) or Windows PowerShell 5.1. No modules needed.

Build from source

Requires the .NET 8 SDK and the WebView2 runtime (already present on current Windows 10/11).

cd SpaceReportApp
dotnet build -c Release

# The single-file release build:
dotnet publish -c Release -r win-x64 --self-contained `
  -p:PublishSingleFile=true -o ..\publish

ui.html and Get-SpaceReport.ps1 are both embedded in the executable and copied next to it. The app prefers the loose copies when they exist, so editing either and rebuilding takes effect immediately; a published single-file build has neither, so it unpacks the embedded ones instead.

To regenerate the icon: pwsh -File SpaceReportApp\make-icon.ps1 To regenerate the screenshots: pwsh -File capture-screenshots.ps1

How it works

The scan is a compiled C# walker (Add-Type) rather than a PowerShell loop, which is the difference between 35 seconds and several minutes for a full drive. It skips reparse points deliberately — following junctions double-counts and can loop forever.

Two Windows quirks worth knowing about, both of which produce plausible-looking wrong answers:

• WinSxS is easy to over-report. Most of its files are hard links that also appear in System32, so any scanner that doesn't detect hard links counts the same bytes twice. Some tools do handle this — WizTree and TreeSize among them. Space Report does not: it sums every file it walks, so its WinSxS figure is inflated the same way. That is why the entry for it points at DISM /Online /Cleanup-Image /AnalyzeComponentStore rather than trusting the number, and why the verdict is NEVER regardless of the size shown
• new DirectoryInfo("C:") means the current directory on drive C:, not the root. The trailing backslash is load-bearing; without it a "full drive scan" quietly reports the working directory instead

Optional: local LLM descriptions

-Ollama sends unrecognised paths to a local Ollama model for a best-effort description, via a helper script named delegate.py placed beside Get-SpaceReport.ps1. It is skipped silently if that file is not present.

Model verdicts are clamped up to REVIEW — a hallucination can never mark something SAFE.

Contributing

The knowledge base is the interesting part, and it is one readable array at the top of Get-SpaceReport.ps1. If the tool reports something as UNKNOWN on your machine and you know what it is, that is a useful pull request.

Rules match on the full path, first match wins, so order matters — put specific patterns above general ones, and anything irreplaceable at the very top.

Licence

MIT — see LICENSE.