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🎶 What's my line? I'm happy cleaning Windows

InstallerClean

An open-source replacement for PatchCleaner. Safely clean up C:\Windows\Installer, the hidden Windows folder that quietly eats your disk space.

Use it once. Maybe save some space. Chuck it away.

• What: Finds and removes unneeded files from C:\Windows\Installer, the hidden folder Windows never cleans up.
• How much space: Only about a third of machines have unneeded files to clean. Of those, the median freed is around 21 GB, and some have cleared hundreds of GB. The other two-thirds find nothing to remove, which simply means their Installer folder is already clean, and the scan takes seconds either way.
• Is it safe: Yes. Only removes files Windows itself says it no longer needs. Delete sends files to the Recycle Bin and never deletes anything permanently without asking. Move is there if you'd rather not take my word for it: it parks the files in a folder of your choice instead.
• Get it: Download the latest release, run it, done.

Contents

• The folder nobody tells you about
• The search for help
• What it does
• Screenshots
• How it works
• Is it safe?
• If you do have a file missing from C:\Windows\Installer
• Accessibility
• What it doesn't do
• FAQ
• Download
• Compared to PatchCleaner
• Command line
• Requirements
• Building from source
• Contributing
• Support the project
• Star history
• Licence

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The folder nobody tells you about

There's a hidden folder on every Windows PC called C:\Windows\Installer. Every time you install software that uses the Windows Installer system, or apply a patch to Microsoft Office, Adobe Acrobat, Visual Studio or any other .msi-based application, a copy of that installer or .msp patch file goes into this folder. And stays there.

When you uninstall the software, the files stay. When a newer patch replaces an older one, both stay. Windows never cleans them up. Disk Cleanup doesn't touch them. DISM is for a different folder entirely. Over the years, the folder grows: 10 GB, 30 GB, 50 GB. On machines with heavy MSI-using software (Acrobat is a frequent culprit), it can pass 100 GB.

These aren't temp files that get recreated the moment you close a cleaning tool. They're genuine dead weight: old installers from software you uninstalled years ago and patches that have been replaced three times over. Once they're gone, they don't come back.

If you're looking for an easy way to free up disk space on Windows, this folder is one of the best places to start. InstallerClean finds the unneeded files and removes them safely.

PatchCleaner has been the go-to tool for this, but it hasn't been updated since March 2016 and it's closed source. InstallerClean is an open-source alternative, with superseded-patch detection (which catches the Acrobat patches PatchCleaner excludes) and a modern UI.

The search for help

If you've ever searched for help with this folder, you know how it goes. Someone asks how to clean it. They're told to run Disk Cleanup. They try it. It frees up 600 MB of a 180 GB folder. The thread goes quiet.

"All of the threads I've found tend to recommend the same things which don't solve the problem, and then go dead."

ksparks519, r/Windows10

Or they're told not to touch it at all. In one thread, someone with a 60 GB Installer folder was told to "don't mess with it." When they asked what they should do instead, the reply was: "I just told you."

The standard advice confuses deleting files at random (which genuinely is dangerous) with removing files that Windows itself says it no longer needs (which isn't). InstallerClean does the latter.

If you've searched for help with this before, you've probably already found PatchCleaner by John Crawford. It's a fantastic app. I downloaded it and it did exactly what it said: freed up a ton of space. The one thing it doesn't handle is Adobe patches; it excludes them by default, and on machines where Adobe is the biggest offender, a lot of removable files get left behind:

"I've downloaded Patchcleaner to delete the orphaned .msp files... 29 GB of the files are 'excluded by filters', so Patchcleaner doesn't seem to help."

HeatherBunny1111, r/techsupport

InstallerClean detects which patches have been superseded by newer updates and flags them as removable, including the Acrobat patches PatchCleaner excludes.

What it does

1. Scans C:\Windows\Installer for .msi and .msp files
2. Queries the Windows Installer API to find which files are still registered
3. Shows what's needed and what's not, with sizes
4. Removes the unneeded files: delete to the Recycle Bin (if it isn't available for the drive, the app asks before any permanent delete), or move to a folder you choose

No automatic network activity. Two opt-in buttons make a single HTTPS call when clicked: Check for updates in About, and Send summary on the completion screen. See What it doesn't do below for the full detail.

Screenshots

Initial scan. This is very quick.

Results: how much is in use, how much is removable.

The files still in use, with metadata read from the installer database.

The files no longer needed.

Confirmation before either action. Delete sends to the Recycle Bin; Move puts the files somewhere of your choice.

After a successful Delete.

After scanning again. Nothing left to clean.

How it works

InstallerClean identifies two kinds of unneeded files.

Orphaned files are installers and patches left behind after you uninstall software. Windows no longer references them, but the files sit in the folder taking up space.

Superseded patches are old .msp patches that have been replaced by newer ones. Windows marks them as superseded in its own database but never deletes them. Vendors that ship frequent patches (Acrobat, Office, large dev tools) accumulate superseded ones indefinitely.

To find them, InstallerClean calls the Windows Installer COM interface directly via P/Invoke:

• MsiEnumProductsEx to enumerate every installed product
• MsiEnumPatchesEx to find all registered patches for each product
• MsiGetPatchInfoEx to read patch state (applied, superseded or obsoleted)

Any .msi or .msp file in C:\Windows\Installer that isn't claimed by a registered product is orphaned. Any patch marked as superseded and not required for uninstall is flagged as removable.

If the API returns incomplete data (rare, but it can happen with corrupted installer state), the app falls back to reading the registry. The fallback only adds files to the "still needed" set, never to the "removable" set.

After a Move or Delete completes, empty subfolders inside C:\Windows\Installer (the directories the cache leaves behind once their contents are gone) are pruned in the same pass. Reparse points are skipped during the prune so a junction planted inside the cache cannot redirect the cleanup outside it.

Is it safe?

Yes. InstallerClean queries the same database Windows itself uses to track what's installed. If Windows says a file is no longer needed, the app trusts it; it doesn't guess based on filenames or dates.

In the app. Delete sends files to the Recycle Bin. If the Recycle Bin isn't available for that drive (it's been turned off for the drive, or it's full or damaged), InstallerClean doesn't quietly delete the files for good. It stops and lets you choose: move them somewhere instead, delete them permanently or cancel. Files are only ever permanently deleted if you explicitly choose that. Move isn't needed for safety, the files are safe to delete; it's there if you'd rather see for yourself first, parking them in a folder you choose for as long as you like. Nothing is touched until you confirm. If Windows Installer is currently writing to the cache, has a previous transaction suspended or has a queued post-reboot rename targeting the cache, Move and Delete are disabled and the specific reason is shown. The scan, query, move, delete, settings and pending-reboot services are covered by an automated test suite that runs on every commit (see the CI badge above).

Verifying the binary. InstallerClean is unsigned. Code-signing certificates cost money annually and I'd rather keep the project free, open and donations-funded.

• SHA-256 hashes for each release are listed on the releases page.
• VirusTotal links for setup, portable, slim and CLI builds are published with each release.
• Source is at github.com/no-faff/InstallerClean and CI builds and tests every commit (see the green CI badge above).
• MajorGeeks tests each submission in a virtual machine and lists it only if it passes their review.
• Softpedia tests each release for viruses, spyware and adware.

VirusTotal: clean across every engine. Live links in each release's notes so you can re-check.

If you do have a file missing from C:\Windows\Installer

InstallerClean only ever clears files Windows reports as finished with, so it can't leave a program unable to repair, update or uninstall. Removing files from C:\Windows\Installer by hand, or with a tool that doesn't check the Installer database first, is a different matter, and it's why the standard advice is to leave the folder alone. That advice is usually right, but not if you use InstallerClean. Here's the fuller picture, and what to do if a needed file has already gone.

About C:\Windows\Installer, and recovering a missing file

C:\Windows\Installer is the Windows Installer cache. When you install an MSI-based program or apply a patch, Windows keeps a copy of the installer here and records, per product, the file it expects to find later. These files aren't used while the program runs; they're used when Windows repairs, updates or uninstalls it. Delete one a program still needs and nothing breaks straight away, which is exactly why it's easy to get away with deleting them and only hit trouble months later. Microsoft puts it like this:

"If the installer cache is compromised, you may not immediately see problems until you take an action such as uninstalling, repairing, or updating a product."

Recovery is not straightforward, and Microsoft is candid about that:

"If application files are missing from the Windows Installer Cache, ask the vendor or support team for the application about the missing files. You must follow the procedures or steps recommended by the application vendor to restore the files. In some cases, you may have to rebuild the operating system and reinstall the application to fix the problem."

"Windows support engineers cannot help you recover missing application files from the Windows Installer cache."

You can't borrow the file from another machine, either:

"Missing files cannot be copied between computers because the files are unique."

In practice, the fix that usually works is to download the affected program's installer from its maker and run it over your existing install. Don't uninstall first: uninstalling is itself one of the steps that needs the missing file. Use the version you currently have installed if you can still get hold of it, because Windows may reject a different one:

"The upgrade cannot be installed by the Windows Installer service because the program to be upgraded may be missing, or the upgrade may update a different version of the program."

This normally restores the file and leaves your settings untouched, but Microsoft doesn't guarantee it, and its documented last resort is reinstalling the program, or rebuilding Windows. That's the official position, reported as I find it. I didn't cause it and I can't improve on Microsoft's own guidance; I'm simply telling you what it is.

None of this can happen because of InstallerClean. It only ever removes files Windows itself reports as no longer needed, so the file a future repair, update or uninstall goes looking for is never one it touched. Microsoft's guidance is at Restore missing Windows Installer cache files.

Accessibility

InstallerClean is built to be fully usable from the keyboard and with a screen reader.

• Keyboard-operable throughout. Tab reaches every control, and the detail-window columns sort from the keyboard, so nothing here needs a mouse. Keyboard focus stays visible wherever it lands.
• Narrator and Voice Access. Every control is labelled, and the visible word on a button is the word that activates it by voice. When a Move or Delete finishes, the outcome is read aloud.
• Built to be read. Text meets WCAG AA contrast throughout the dark theme.

If anything here gets in your way, open an issue. Accessibility problems are bugs, not edge cases.

What it doesn't do

• WinSxS (C:\Windows\WinSxS) is a different folder with different rules. For that one, run Dism /Online /Cleanup-Image /StartComponentCleanup from an elevated prompt.
• No background service, no scheduled task, no auto-clean. The app runs when you launch it.
• The registry is read-only. The app queries the Windows Installer database; it doesn't change it.
• No automatic telemetry, no background network. The app makes no network call until you click one of two buttons. Check for updates in About queries GitHub's public releases API on click and tells you whether you have the latest version (single HTTPS GET, identifying string InstallerClean/<version>). Send summary on the completion screen reads %LOCALAPPDATA%\NoFaff\InstallerClean\last-run.json and HTTPS-POSTs it to a No Faff endpoint so I can see whether the run worked. The JSON contains counts and categorical labels only: no file paths, no user names, no machine identifiers, no time-of-day. Clicking opens a confirmation window showing the exact JSON about to be sent; review it there and press Send to confirm, or Cancel to back out. Once per machine: after a successful send the button stays hidden for ever; if the first attempt fails with a transient error the next session re-prompts.
• No bundled extras. No toolbars, no third-party offers, no upsells.
• The only permission asked for beyond launching is Administrator, which is required because C:\Windows\Installer is admin-only.

FAQ

Will I actually free up GBs of space? Depends on your machine. A clean Windows 11 install with no extra software has nothing to remove. A long-running developer workstation, or any machine with heavy MSI-based software (Acrobat, Office, LibreOffice, large dev tools), can have tens of GB. Run installerclean-cli /s to see exactly what would be removed before you commit.

Across the 73 reports people have been kind enough to send in (thanks 🙏) since v1.8.0 added the option:

Outcome	Share	Smallest	Median	Largest
Nothing to remove	66%	-	-	-
Freed space	34%	0.2 GB	23 GB	327 GB

Here's what a report looks like

{
  "schemaVersion": 3,
  "app": { "version": "1.9.0" },
  "os": "Windows 11 (X64)",
  "scan": {
    "durationMs": 1820,
    "registeredCount": 148,
    "orphanedCount": 40,
    "supersededCount": 25,
    "obsoletedCount": 5,
    "missingFromDiskCount": 0,
    "pendingReboot": "clean"
  },
  "operation": {
    "kind": "delete",
    "outcome": "complete",
    "filesProcessed": 70,
    "filesFailed": 0,
    "bytesFreed": 22548578304,
    "errors": [],
    "moveDestinationKind": null
  }
}

It carries counts and categorical labels only: no file paths, no user names, no machine identifiers.

Why does it want Administrator? C:\Windows\Installer is owned by SYSTEM and locked down to admins only. Reading the folder, writing to the Installer-database query API and moving or deleting files all require elevation. There's no user-mode path.

Can I undo a Delete? Usually, yes. When the Recycle Bin is available for the drive, Delete sends files there and you can restore them from the bin. If the bin isn't available, the app never deletes for good on its own (see Is it safe?). And if you'd rather have a way back you control, Move puts the files in a folder you choose; delete them from there whenever you're satisfied.

Will Windows complain if I remove these files? No. InstallerClean only ever removes the files Windows itself reports as finished with, so nothing it removes is needed to repair, update or uninstall a program. If a needed file does go missing from C:\Windows\Installer by some other means, see If you do have a file missing from C:\Windows\Installer.

Why no Win32_Product (WMI)? Win32_Product triggers MSI repair operations on every product during enumeration, which can take minutes and load the disk hard. InstallerClean calls the Windows Installer COM API directly with no side effects.

Why not just a PowerShell script? A short script that calls MsiEnumPatchesEx is enough to list patches, but the load-bearing parts of InstallerClean are the bits a script glosses over: the orphan-vs-superseded classification, the registry fallback that only ever adds files to the "still needed" set (never to "removable"), the pending-reboot block, the Move-to-elsewhere safety net, the per-file progress with cancellation and the Recycle-Bin-not-permanent-delete default. Edge cases on real heavy-MSI machines (corrupt registrations, junctions inside the cache, products in HKU\.DEFAULT, suspended Installer transactions) are easy to mishandle in a one-off script. The installerclean-cli is the headless face if scripting is what you want.

Does it work on Windows 7 or 8? Untested and not supported. Targets Windows 10 and 11.

Is it suitable for RMM / mass deployment? Yes. The CLI exits with distinct codes per outcome (0 success, 2 partial, 1 hard failure, 75 transient, 130 Ctrl+C) so a scheduled task can retry on 75 without conflating it with hard failures. It writes a per-run summary to the Application event log and respects the same single-instance mutex as the GUI. See the Command line section.

Download

Four builds, choose one:

• Setup (InstallerClean-setup.exe): a regular Windows installer with the .NET 10 runtime bundled. Adds a Start Menu entry and uninstalls cleanly. Tucked into Programs so it's easy to find six months from now.
• Portable (InstallerClean-portable.exe): a single self-contained exe with the runtime bundled. No install, no uninstaller. Run it, use it, delete it. Run it again whenever.
• Slim (InstallerClean-slim.exe): the smallest download. Requires the .NET 10 Desktop Runtime to be installed already (which you have if you have an up-to-date Visual Studio).
• CLI (installerclean-cli.exe): the command-line version on its own, a single self-contained exe. No install, nothing left on the machine afterwards. Drop it on a client, run a scan or a clean, delete it. Built for scripting, scheduled tasks and mass deployment, where you want the operations without a desktop app on the client. See Command line for the arguments and exit codes.

Download from the releases page, then run. Windows SmartScreen will say "Unknown publisher". Click More info then Run anyway. This is normal for unsigned open-source software.

The app scans automatically on startup. Review the results, then click Delete or Move.

Or install via Scoop:

scoop bucket add no-faff https://github.com/no-faff/scoop-bucket
scoop install installerclean

Compared to PatchCleaner

	InstallerClean	PatchCleaner
Last updated	2026 (active)	3 March 2016
Source code	Open source (MIT)	Closed source
Runtime	.NET 10 (self-contained)	.NET + VBScript
API	Windows Installer COM (in-process)	Windows Installer COM (out-of-process via VBScript)
Superseded patch detection	Yes	No
Adobe handling	Detects superseded patches	Excludes by default
UI	Dark theme (WPF)	Windows Forms
Data collection	None	None
Delete safety	Recycle Bin, never a silent permanent delete	Permanent, no Recycle Bin

A note on Win32_Product: The common-but-broken approach for listing installed products is Win32_Product (WMI), which triggers MSI repair operations on every product during enumeration. Both InstallerClean and PatchCleaner avoid it. Both use the Windows Installer COM interface. The WMIProducts.vbs filename in PatchCleaner's script is misleading; the script uses MSI COM, not WMI.

Ultra Virus Killer (UVK) also offers Installer cleanup as part of its System Booster module, but it's a paid tool ($15-25) and the cleanup is one small feature inside a much larger application. InstallerClean is free, focused and open source.

General-purpose system cleaners like CCleaner and BleachBit do not touch C:\Windows\Installer. The folder needs Windows Installer API queries to tell registered packages from unneeded ones, and a generic cleaner that just walked the file tree could break installed apps. InstallerClean is the tool to reach for when that's the folder you actually want cleaned.

Command line

InstallerClean supports headless operation for scripting and sysadmin use:

Usage:
  installerclean-cli --help   Show this help (also accepts /?, -h)
  installerclean-cli --version  Print the version (also accepts -v)
  installerclean-cli /s       Scan only - list removable files
  installerclean-cli /d       Delete removable files (Recycle Bin)
  installerclean-cli /m       Move to saved default location
  installerclean-cli /m PATH  Move to specified path

To launch the GUI, run InstallerClean.exe (or use the Start-menu shortcut from the setup install).

Run with no argument, or an unrecognised flag, and installerclean-cli prints this usage and exits 1, so a scheduled task that drops its flag fails visibly instead of silently succeeding while doing nothing. An explicit --help, /? or -h prints the same usage and exits 0.

/s is a dry run: it scans, lists what it would remove with filenames and sizes, then exits. Useful for auditing before cleanup. Exit code is 0 on a successful scan, 1 if the scan fails and 130 on Ctrl+C. All files are in C:\Windows\Installer.

/d and /m scan and then act. /d sends removable files to the Recycle Bin. /m moves them to a folder (either one you specify on the command line, or the default saved from the GUI). Exit codes: 0 for full success, 2 for partial (some files succeeded, some failed), 1 for total failure (scan failed, bad arguments or every file in the batch failed), 75 for a transient condition that blocked the run (the printed message explains which and whether a retry will help), 130 for Ctrl+C.

All of the CLI's output, including error and diagnostic messages, goes to stdout; there is no separate stderr stream. The exit code is the machine-readable signal (and the per-run Application event log entry mirrors it), so a script should key off the exit code rather than parse the text, and installerclean-cli /s > audit.txt captures the whole run including any error line.

All three require an elevated (administrator) command prompt. If Group Policy blocks the UAC elevation prompt the process refuses to start and Windows returns error 740 to the parent shell ($LASTEXITCODE = 740 in PowerShell). taskkill /pid <pid> does not fire a graceful cancel; the single-instance mutex is recovered by the next run via the AbandonedMutexException path.

Why installerclean-cli and not installerclean.exe?

InstallerClean.exe is the WPF GUI; it does not respond to command-line arguments. installerclean-cli.exe is a separate console executable that ships in the same install directory and exposes the same scan / move / delete operations to PowerShell, cmd and scheduled tasks. Because it is a real console process, it blocks the prompt until it finishes; redirect or pipe its output as you would any other console exe.

The portable and slim downloads contain only the GUI exe. If you want the command line without the GUI, download installerclean-cli.exe from the releases page and run it directly. The setup installs it alongside the GUI as well.

Requirements

• Windows 10 or 11
• Administrator privileges (C:\Windows\Installer is admin-only)

See Download for setup, portable, slim and CLI build options.

Building from source

git clone https://github.com/no-faff/InstallerClean.git
cd InstallerClean
dotnet build src/InstallerClean/InstallerClean.csproj

Run the tests:

dotnet test src/InstallerClean.Tests/

Contributing

Found a bug or have a suggestion? Open an issue or start a discussion. Pull requests welcome. Please run dotnet test before submitting.

Support the project

If InstallerClean helped, consider supporting No Faff or leaving a star on GitHub.

Star history

Licence

MIT

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🎶 George Formby - When I'm Cleaning Windows. Enjoy!