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🎶 What's my line? I'm happy cleaning Windows
An open-source tool to 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: InstallerClean does one thing: it removes unneeded files from
C:\Windows\Installer, a hidden folder Windows never cleans up. After a nearly instant scan it tells you whether you have any, shows more detail for the curious, and lets you delete them to free up space on your C: drive. You use it once and move on. - How much space: The (optional) reports sent in so far show 41% of machines had unneeded files to clean. Of those, the median freed is 22 GB. A few cleared hundreds of GB. For me it was 1.28 GB. The other 59% found nothing to remove, which just means their Installer folder was already clean. More detail in the FAQ below.
- Is it safe: Yes. It asks the Windows Installer API itself which files are still needed and only ever lists the ones Windows reports as finished with. It's open source (MIT) and asks nothing about you: no account, no ads, no tracking, no telemetry, nothing running in the background. It never goes online by itself.
- Get it: Download the latest release. Run it; click through Windows's warning and the admin prompt. Delete any unneeded files. Done.
- 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
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 time, the folder grows: 1 GB, 5 GB, 20 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 come back on their own. They're genuine dead weight: old installers from software you uninstalled years ago and patches that have been replaced several 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 a good place to start. InstallerClean finds the unneeded files and removes them safely.
If you've ever searched for help with this folder, you probably know how it goes. Someone with 180 GB in C:\Windows\Installer asks how to clean it. They're told to run Disk Cleanup. They try it. It clears 600 MB, none of it from that folder (because Disk Cleanup doesn't touch C:\Windows\Installer). 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."
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.
- Scans
C:\Windows\Installerfor.msiand.mspfiles - Queries the Windows Installer API to find which files are still registered
- Shows how much you can free and how much is still needed, with optional detail windows listing every file
- Removes the unneeded files: delete to the Recycle Bin, or move to a folder you choose
Initial scan. This is very quick.
Results: how much is still needed, how much is removable.
Details of the files still needed, with metadata read from the installer database.
Details of 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.
InstallerClean identifies three kinds of unneeded files.
Orphaned files are the .msi installers (and any .msp 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.
Obsoleted patches are .msp patches the publisher has withdrawn or deprecated rather than replaced with a newer version. Windows records that state too, and likewise leaves the file in the folder.
To find them, InstallerClean calls the Windows Installer COM interface directly via P/Invoke:
MsiEnumProductsExto enumerate every installed productMsiEnumPatchesExto find all registered patches for each productMsiGetPatchInfoExto 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 and flagged as removable. So is any patch the database marks superseded or obsoleted that isn't required for uninstall.
If the API returns incomplete data (rare, but it can happen with a 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.
Yes. InstallerClean queries the same Windows Installer API database that 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.
About Delete and Move. The files InstallerClean deletes are safe to delete permanently. Delete sends them to the Recycle Bin (you'll be warned if it's not available); you gain the space back on your C: drive when you empty your Recycle Bin.
You don't have to trust me that the files are safe to delete, though. While they're in your Recycle Bin, you have a chance to check that the apps that use this folder, Office, Acrobat, Visual Studio and the like, still update and uninstall without trouble. If anything's broken (it won't be!), restore the files from the Recycle Bin to fix it. To be super safe, you can instead use Move - to park the files in a folder of your choice (obviously choose a folder on another partition/drive if you're looking to free space on C:). Just copy the files back to C:\Windows\Installer to restore things back to how they were (but you won't need to!).
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, so you don't have to take it on trust:
- SHA-256 hashes for each release are listed on the releases page.
- VirusTotal: clean across every engine. Live links in each release's notes so you can re-check.
- Source is at github.com/no-faff/InstallerClean and CI builds and tests every commit (see the green CI badge above).
- 23k downloads across GitHub, MajorGeeks and Softpedia.
- 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.
InstallerClean only removes files Windows itself reports as no longer needed, so it can never be the reason a file is missing. But if one has already gone, InstallerClean spots it and flags it. Here's the fix.
Download that program's installer from its maker and run it over your existing installation; don't uninstall first. Use the version you have now if you can, because Windows may turn down a different one. That usually puts the file back and leaves your settings alone. Re-scan in InstallerClean and the warning will be gone if it worked.
That usually works. What follows is Microsoft's own, fuller account: the official detail, and the harder cases for when it isn't that simple. None of it is InstallerClean's doing, and I can't improve on Microsoft's guidance, so I'm just passing it on.
Microsoft's fuller position
Full guidance: Restore missing Windows Installer cache files.
It may not show up straight away:
"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."
The files are unique per machine, so you can't copy one from another PC:
"Missing files cannot be copied between computers because the files are unique."
You can't pull just the file from a backup, either:
"To restore the missing files, a full system state restoration is required. It is not possible to replace only the missing files from a previous backup."
The recommended recovery, and its blunt limits:
"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."
Why the same version matters:
"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."
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.
- WinSxS (
C:\Windows\WinSxS) is a different folder with different rules. For that one, runDism /Online /Cleanup-Image /StartComponentCleanupfrom 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.
- It only connects to the internet when you tell it to: a manual update check; the optional anonymous summary (just to let me know it's working); and links to the GitHub docs and a donate page, which open in your browser if you choose to click them.
- No toolbars, no bundled software, no adware.
Will I actually free up GBs of space? It 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. Either way, you'll see exactly how much the moment you run it.
Across the 85 reports people have sent in (thanks 🙏) since v1.8.0 added the option:
| Outcome | Share | Smallest | Median | Largest |
|---|---|---|---|---|
| Nothing to remove | 59% | - | - | - |
| Freed space | 41% | 0.1 GB | 22 GB | 327 GB |
Those reports come from the optional "Send summary" button. Here's what you'll see before anything's sent.
Why does it want Administrator? C:\Windows\Installer is locked down to administrators. Reading it, querying the Installer database and moving or deleting files all need that, so the app has to run as admin.
Why does Windows say "Unknown publisher"? Because InstallerClean isn't code-signed. A signing certificate costs money every year, and I'd rather keep the app free than pay for one. So when you run it, Windows SmartScreen shows "Windows protected your PC". Click More info, then Run anyway. It's safe to do: the source code is public, and every release has VirusTotal links and SHA-256 hashes you can check first.
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 for a Ctrl+C before any file was processed; a Ctrl+C that lands mid-batch exits 2, since work was committed) 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. The setup also installs silently with the standard Inno Setup switches (/SILENT or /VERYSILENT); the post-install launch is skipped on silent installs. See the Command line section.
Three 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. - 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. It's unsigned, so Windows shows an "unknown publisher" warning; the FAQ explains what you'll see and why it's safe.
The app scans automatically on startup. Review the results, then click Delete or Move.
Or install via winget:
winget install NoFaff.InstallerClean
Or install via Scoop:
scoop bucket add no-faff https://github.com/no-faff/scoop-bucket
scoop install installerclean
If you've searched for this folder before, the tool you'll most likely have found is PatchCleaner. It's still going strong, but I made InstallerClean because PatchCleaner is closed source, hasn't had an update since March 2016 and, by default, won't touch Adobe products. Its orphan check wrongly flagged Adobe's patches, and removing them broke Adobe's updates, so it leaves all Adobe files alone unless you switch the filter off. On the machines where Adobe is the worst offender, that's most of the space:
"I've downloaded Patchcleaner to delete the orphaned .msp files, but apparently this would only free up 250 MB of space. 29 GB of the files are 'excluded by filters', so Patchcleaner doesn't seem to help."
HeatherBunny1111, r/techsupport
InstallerClean reads the Windows Installer's own patch records, so it can tell which Adobe patches are genuinely superseded and clear those safely, with no blanket filter. Here's how the two compare:
| 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. If it isn't available, it asks: move instead or delete permanently | Permanent, no Recycle Bin |
A note on
Win32_Product: The common-but-broken approach for listing installed products isWin32_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. TheWMIProducts.vbsfilename 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.
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 a Ctrl+C before any file was processed (a Ctrl+C that lands mid-batch exits 2, partial, since work was committed).
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.
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 download contains 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.
- Windows 10 (version 1607 / build 14393 or later, the oldest the .NET 10 runtime supports) or Windows 11
- Administrator privileges (
C:\Windows\Installeris admin-only)
See Download for setup, portable and CLI build options.
git clone https://github.com/no-faff/InstallerClean.git
cd InstallerClean
dotnet build src/InstallerClean.sln
Run the tests:
dotnet test src/InstallerClean.Tests/
Found a bug or have a suggestion? Open an issue or start a discussion. Pull requests welcome. Please run dotnet test before submitting.
If InstallerClean helped, consider supporting No Faff or leaving a star on GitHub.