Windows 10 & 11 SSD Filling Up? Safely Clean Windows.old, WinSxS, Update Cache and AppData

His findings are useful, but a few of his claims need correcting or qualifying against Microsoft's documentation. Here is each folder, what it does, and the safest way to reclaim space.

First, a reality check on Storage Sense​

Storage Sense is not a general-purpose space reclaimer. Microsoft's documentation says that with default settings it runs when the device is low on disk space and cleans up unnecessary temporary files. The same page says the Downloads folder and cloud content aren't touched unless you configure Storage Sense to manage them.

Microsoft also says it works on the system drive only. That is usually C:. So Storage Sense can be on and your SSD can still bloat. It was never promised to clear the folders below.

Windows.old: the rollback safety net​

Windows.old holds files from your previous Windows installation. Windows creates it during certain upgrades so you can roll back. The author says it can take roughly 10 to 35GB. Treat that as his observation, not a guarantee.

Microsoft says that ten days after you upgrade, your previous version of Windows is automatically deleted. If you want the space sooner, Microsoft documents a Settings route:

1. Open Settings > System > Storage.
2. Under your drive information, select Temporary files.
3. Tick the previous Windows version entry and select Remove files.

The wording differs between Microsoft pages. One says "Previous version of Windows" and another says "Previous Windows Installation(s)". Look for whichever label your build shows.

Two cautions:

• Deletion is permanent. Microsoft warns that if you delete your previous version of Windows, this can't be undone, so you lose the ability to go back.
• You need administrator rights. Microsoft notes the action requires them.

The MakeUseOf piece also recommends Disk Cleanup with "Clean up system files". Disk Cleanup is a legacy tool and can still work. For a current Windows 10 or 11 install, the Settings route is the one Microsoft documents for this task.

One correction to the original article: it places C:\Windows\WinSxS directly after the Windows.old discussion. These are two separate locations. Windows.old is the previous-installation folder. WinSxS is the component store, covered next.

WinSxS: big-looking, but not yours to delete by hand​

WinSxS is the component store. Windows uses it to service the OS, install updates, toggle features and repair problems. The author's folder showed about 18GB. After cleanup it showed roughly 10GB, so he recovered about 8GB. That is one laptop's result. Your savings could be far smaller.

Microsoft's guidance is blunt. Deleting files from WinSxS or deleting the entire folder may severely damage your system so that your PC might not boot and make it impossible to update. Use the built-in tools instead.

Windows already trims the folder itself. Microsoft says previous versions of some components are kept for a period of time so you can roll back if necessary, then removed automatically. The scheduled cleanup task waits at least 30 days after an updated component is installed before removing earlier versions. If you run that task manually, it has a one-hour timeout and may not finish.

For an on-demand cleanup, run this from an elevated Command Prompt:

Dism.exe /online /Cleanup-Image /StartComponentCleanup

Microsoft says this gives similar results to the scheduled task. The differences are that previous versions of updated components are deleted immediately, with no 30-day grace period, and there is no one-hour timeout.

Think twice about /ResetBase​

You will see /ResetBase suggested online as the stronger option. Microsoft documents it, but with a real trade-off. It removes all superseded versions of every component. After it completes, all existing update packages can't be uninstalled. Future updates are not blocked from uninstalling. For a home PC where you want a few GB back, the basic command is usually the safer choice. If you manage machines, factor that rollback loss into your servicing policy.

Folder sizes can mislead​

Explorer and disk analyzers can report the size of WinSxS in ways that don't reflect its true footprint. Microsoft links separate guidance, "Determine the actual size of the WinSxS folder", for this reason. So treat a scary number in WizTree as a prompt to investigate, not as proof of waste.

SoftwareDistribution\Download: the update staging area​

Windows stores downloaded updates here before installing them. The author's copy was under 100MB, though he says it can reach 15GB. Even in his case it was small. Check yours before assuming it's a problem.

The procedure he describes is:

1. Stop the Windows Update service (for example from services.msc).
2. Open C:\Windows\SoftwareDistribution\Download and delete the contents. Leave the Download folder itself.
3. Restart the Windows Update service.

Independent how-to guides describe the same stop, delete and restart sequence. One notes that if any files are in use, you should restart the computer and try again. Don't clear the cache while an update is actively downloading or installing.

Context the original leaves out​

Microsoft frames clearing the update cache as a troubleshooting step, listed under "Clear the Windows Update Cache" for update problems. It is not a recommended routine chore. Windows rebuilds what it needs, so you aren't breaking anything. But if this folder is small, clearing it gains almost nothing.

Clearing it also doesn't uninstall updates you've already installed. Microsoft says removing an installed update is a separate action in update history, and that not all updates can be removed.

Also, don't confuse this cache with component cleanup. One guide notes that component store cleanup doesn't clear the active SoftwareDistribution download cache. That makes them two different fixes.

AppData: the biggest wildcard​

The author says AppData deserves the most attention. Depending on your apps, he says it can reach tens of gigabytes, and over 100GB on some systems. That depends heavily on what you run. Browsers, messaging apps, game launchers and creative tools all store caches, logs and temporary files here.

The path is C:\Users\[YourName]\AppData, and Windows hides it by default. Microsoft's profile-directory documentation says some profile directories are hidden by default. You can view them with the Show hidden files, folders, and drives option.

A precision note on %localappdata%​

The article suggests %localappdata% in the Run dialog (Win + R). That is handy, but it opens the Local subfolder, not the whole AppData tree. AppData also contains Roaming, and LocalLow often appears alongside Local. If you're hunting for space, check which subfolder is actually large before touching anything.

Delete selectively, not wholesale​

The author says clearing the folder resets app settings and logins, and recommends deleting only files for apps you rarely use. The caution is sound, but the effects vary by app.

Microsoft's documentation for packaged apps separates app data into categories. It describes the local cache folder as holding things like cached files, logs and authentication tokens. In contrast, the temporary folder isn't guaranteed to persist across sessions and can be deleted by the system at any time. That distinction is for packaged apps. Traditional desktop apps follow their own rules.

A safer approach:

1. Close the app first.
2. Find which app's folder is large.
3. Use the app's own cache or storage controls where available, such as a browser's clear-cache option.
4. Only then consider deleting that app's folder, and expect to sign in again.

Suggested cleanup order​

1. Open Settings > System > Storage and look at the categories and cleanup recommendations first.
2. Remove the previous Windows installation only if you're sure you won't roll back.
3. Run the basic DISM component cleanup if the component store looks bloated.
4. Clear the update download cache if it's large or updates are failing.
5. Trim AppData per app, starting with browser caches.

What this means for you​

The article's practical lesson holds up. System folders can quietly absorb space, and a disk analyzer is a good way to find them. But the headline numbers are one user's experience. They aren't benchmarks, and Microsoft doesn't promise any particular recovery.

Some of the "hidden hoarders" are also Windows doing what it was designed to do. Rollback files and component history exist so you can recover from a bad update. Deleting them early trades that safety net for free space. On a 512GB drive that trade may be worth it, but you should make it knowingly.

Pay attention to the one thing Microsoft is emphatic about: never hand-delete WinSxS. Everything else here is either self-cleaning, rebuildable or, in the case of AppData, a matter of knowing which app you're clearing.