Folder Size Explorer — free disk space analyzer for Windows

Find out what's eating your disk space. Folder Size Explorer is a tiny, portable folder size analyzer for Windows: browse any drive or folder and instantly see the size of every subfolder, ranked and drawn as a usage bar. No installer, no telemetry, no admin rights — a single 31 KB .exe that runs on any Windows machine with .NET Framework 4.8 (which means: every Windows 10 and Windows 11 install, out of the box).

Download

Grab FolderSizeExplorer.exe from the Releases page and run it. That's the whole installation — it's portable, writes nothing to the registry, and works fine from a USB stick.

Features

• Per-folder sizes computed recursively in the background, with a live progress bar
• Usage bars — a relative bar per row, so the space hogs jump out without a treemap
• Sortable columns — name, size, item count, last modified
• Drive overview with total / free / used space on hover
• Cancel any time — scanning a slow network share never locks the UI
• Right-click → Open in Explorer from either the tree or the list
• Per-monitor DPI aware — stays crisp on mixed-DPI multi-monitor setups
• Portable — one file, no installer, no dependencies, no admin rights

How it compares

There are excellent disk space analyzers for Windows already — WinDirStat, WizTree and TreeSize Free are the usual recommendations, and if you want treemaps or raw NTFS-MFT scanning speed, use those.

Folder Size Explorer is deliberately smaller in scope:

	Folder Size Explorer	Typical alternatives
Install	Single 31 KB exe, portable	Installer or multi-MB portable bundle
Admin rights	Not required	Often required (MFT access)
View	Explorer-style tree + sortable list with usage bars	Treemap, or a heavier grid
Dependencies	.NET Framework 4.8 (built into Windows)	Bundled runtimes
Source	MIT, ~600 lines of C# you can read in one sitting	Larger codebases

Use it when you want to answer "which folder is eating my C: drive?" in a few seconds without installing anything.

Frequently asked questions

How do I see which folder is taking up the most space on Windows?

Run Folder Size Explorer, pick the drive, and sort by the Size column. Folder sizes are calculated recursively, so a folder's row includes everything nested beneath it. Windows File Explorer deliberately doesn't show folder sizes — that's the gap this fills.

Does it need to be installed?

No. It's a single portable executable. Download, double-click, done. Delete the file to uninstall.

Does it need administrator rights?

No. It reads the filesystem with your own permissions. Folders you can't access are skipped and reported rather than crashing the scan.

Is it safe / does it phone home?

There is no network code in it at all — the source is a single readable C# file in src/FolderSizeExplorer. Every release binary is built by GitHub Actions from this repository, so you can match the release to the commit that produced it.

Will it delete files for me?

No. It's read-only by design. It shows you where the space went and opens folders in File Explorer so you can decide what to remove yourself.

Does it work on Windows 10 / Windows 11 / Windows Server?

Yes — anything with .NET Framework 4.8, which ships with Windows 10 (1903+), Windows 11 and current Windows Server releases.

Building from source

Requires the .NET SDK 8.0 or newer on Windows.

build.cmd

or directly:

dotnet build src\FolderSizeExplorer\FolderSizeExplorer.csproj -c Release

Output: build\FolderSizeExplorer\Release\FolderSizeExplorer.exe

Every push to main builds the same way on GitHub Actions and uploads the exe as a workflow artifact; pushing a v* tag publishes a GitHub Release.

Repository layout

.
├─ .github/workflows/build.yml   CI: builds the exe on every push
├─ src/FolderSizeExplorer/       application source
│  ├─ FolderSizeExplorer.cs      UI + scanning logic
│  ├─ FolderSizeExplorer.csproj  project file (net48, WinExe)
│  ├─ FolderSizeExplorer.ico     application icon
│  └─ app.manifest               per-monitor DPI awareness
├─ build/                        build output (git-ignored)
├─ Directory.Build.props         keeps bin/obj out of src/
└─ build.cmd                     local release build

Contributing

Issues and pull requests are welcome. The whole application is one C# file — no build system to learn, no framework to fight.

License

MIT — see LICENSE. Free for personal and commercial use.

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