Microsoft sleeping

[SynapseScribe]

Why isn't windows cleaning up by default? I was surprised to release 12 GB from my precious ssd. This is just nuts

[SynapseScribe]

btw you can add my 12 GB to the report, i didn't send it

[FarmLox]

Hey, @SynapseScribe, thanks for getting in touch.

Why isn't windows cleaning up by default? I was surprised to release 12 GB from my precious ssd. This is just nuts

It's a very good question and gets to the heart of InstallerClean's raison d'être.

As far as I can tell, Microsoft has never answered it.

All the Microsoft sources I've found explain why the needed files are kept, but none explain why Windows doesn't clean up the unneeded ones.

Here's what I know.

1. Someone asked Microsoft this exact question and got a non-answer.
https://learn.microsoft.com/en-us/answers/questions/2777465/my-windows-installer-folder-is-over-90-gb-does-mic
Question title: "My windows installer folder is over 90 GB. Does Microsoft have a safe way to get rid of orphaned installer files?"
The Microsoft-side reply, in full: "We don't recommend removing files in the Windows Installer folder or directory as it may cause serious problems in your computer."
That's it. Asked point blank about orphaned files, Microsoft answered about files in general, offered nothing, and pointed at the Feedback Hub.

2. Microsoft's own Q&A tells people to use a third-party tool. A tacit admission that Windows won't do it.
https://learn.microsoft.com/en-us/answers/questions/5540026/orphaned-installer-please-help-to-deuce-amount-of
Ramesh Srinivasan (Independent Advisor, a community volunteer, not Microsoft staff): "The C:\Windows\Installer folder is required for software updates. However, there may be orphaned .msi and .msp files in that folder that can be cleared. You can use PatchCleaner (freeware) to identify and remove orphaned .msi packages in that folder."

InstallerClean essentially does what PatchCleaner does (and a bit more). I built InstallerClean because PatchCleaner hadn't seen an update since March 2016.

3. The nearest thing to a stated reason, and it's a guess by a volunteer, not Microsoft.
https://learn.microsoft.com/en-us/answers/questions/5854721/why-doesn-t-windows-include-a-built-in-tool-to-cle
Same Ramesh Srinivasan: "That's probably why Microsoft discontinued its legacy cleanup tools, such as Microsoft RegClean or MSIZap, two decades ago. The risks of cleanup outweigh the benefits."
Note that Ramesh is not Microsoft, he says "probably" so he's speculating, and the question is about app leftovers generally rather than the Installer folder. (The second answer on that page is flagged as AI-generated, so I'm ignoring that.)

4. Microsoft did once ship a cleanup tool, then killed it. The Windows Installer CleanUp Utility (msicuu2.exe, KB 290301), pulled from the Download Center in June 2010.
https://learn.microsoft.com/en-us/answers/questions/2498465/the-microsoft-installer-cleanup-utility-has-been-r
Their stated reason: it "sometimes damaged other components installed on the computer."

Note that it wasn't doing the job InstallerClean does. msicuu2.exe was only a GUI shell. The engine underneath was msizap.exe, and what the GUI put in front of users was the dangerous half: it ripped out a product's Windows Installer registration, the bookkeeping, without running a real uninstall. Microsoft's own words: "Msizap.exe is not magic, but merely a tool that acts only on Windows Installer registration data. It will not run the removal actions." (https://devblogs.microsoft.com/setup/msizap-is-not-uninstall/) So the removal steps never ran and stale registration got left behind, which could then break other software, or a newer version of the same software. Their own example is zapping .NET 2.0: the actions that unregister the incompatible WMI providers never run, that registration sticks around, and it breaks what comes next. Hence "damaged other components".

msizap.exe also had a /G switch, and that one removed orphaned cached Installer files - the actual disk-space job. By common consent it was the only genuinely safe switch on the thing, and it was never what the GUI exposed. So when Microsoft retired the utility in 2010, the safe orphan cleanup went in the bin along with the dangerous registration surgery, and nothing has replaced it since.

Microsoft had the safe half, bundled it with a dangerous half, binned the lot, and never built it back.

So how confident am I that InstallerClean won't "sometimes damage other components installed on the computer"? Completely, and for a structural reason rather than a promise. What made Microsoft's tool dangerous was that it wrote to Windows Installer's own records, tearing a program's registration out from under it. InstallerClean never writes to them. It only reads them, to ask which cached files something installed still points to, and then it touches nothing but the files that nothing points to. It removes no registration, no component, no reference count, and it never leaves Windows Installer's bookkeeping in a state Windows didn't put it in. The failure that killed msicuu2.exe isn't something InstallerClean is capable of doing.

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Then regarding

btw you can add my 12 GB to the report, i didn't send it

I'd love to, because yours (and one other person's report a while back) would bring the per cent of people who had unneeded files to clean up to more than 50% and the higher that number is, the more worthwhile InstallerClean is! But I'd be bodging the json reports that have got sent in. So thanks a lot but I'll just let it slide and be pleased that my figures underplay how many people have reported InstallerClean being useful.

All the best. I'm very glad to hear that my tool's freed up 12 GB on your precious ssd.