The regenerables: temp files and caches
The safest deletions on any Windows PC are scratch files that applications rebuild on demand: %TEMP% (yours under %LOCALAPPDATA% and the system one at C:\Windows\Temp), the Windows Update cache at C:\Windows\SoftwareDistribution\Download, which is nothing but packages that have already been installed, and the Delivery Optimization cache — fragments of updates already shared with other PCs. Emptying the update cache is safe at any time and occasionally unsticks an update that refuses to finish. The same goes for browser caches, the DirectX shader cache, and the thumbnail databases Explorer keeps for every folder: delete them and the worst case is images reloading from the network, shaders recompiling on first launch, thumbnails redrawing themselves.
Crash diagnostics belong in the same bucket, with one honest caveat: delete them after you've reported — or decided to ignore — the crash. C:\Windows\Minidump, the memory.dmp file in C:\Windows, and the Windows Error Reporting archive under ProgramData\Microsoft\Windows\WER are pure telemetry leftovers — memory.dmp alone can match your RAM size, so on a machine with recurring crashes these quietly pile up gigabytes. Once the report has been sent, nothing on your PC needs those files back.
The one-time gains: installers, Windows.old and the Recycle Bin
The bigger, less frequent wins come from files nobody will ever need again. A Downloads folder used as a junk drawer for years typically hides several gigabytes of installers for app versions nobody runs anymore. Windows.old — the previous Windows kept for rollback after a feature update — routinely weighs 20–30 GB, and ten days after an upgrade you're happy with, it's pure dead weight. And the Recycle Bin is "deleted" files still paying rent: emptiness there is real space back.
- %TEMP% and C:\Windows\Temp — scratch files apps abandoned; skip whatever is in use today, take the rest
- Old installers in Downloads (.exe and .msi of apps you already have, in versions you'll never install)
- Windows.old, ten days after a feature update you're happy with — it exists only for rollback
- C:\Windows\SoftwareDistribution\Download — update packages that have already been installed
- The Recycle Bin — a "delete" that never happened is still space spent
- Crash dumps and WER archives — memory.dmp alone can be the size of your RAM
The two-second rule that keeps deletions safe
The rule is simple: if you can name where a file comes from and you know Windows or an app regenerates it, delete freely; if you can't, leave it alone — disk space is cheaper than a broken app. Never touch anything inside Windows, Program Files or a program's data folder beyond the caches named above, and treat AppData and ProgramData as "known caches only" territory. When in doubt, delete to the Recycle Bin and live with it for a week before emptying; problems surface fast. Storage Sense in Settings → System → Storage automates most of this list on a schedule, and a dedicated cleanup tool like Kleaner PRO walks the same list in one pass — routines stick, one-shot purges fade.
Questions and Answers
Is it safe to delete files in the Temp folder?
Yes — %TEMP% is scratch space by definition, and apps expect it to be emptied. If a file is in use, Windows will refuse to delete it; skip that one and take the rest.
How do I free up space without deleting anything important?
Start with Settings → System → Storage → Temporary files, which lists every safe category with checkboxes, then move on to Downloads and Windows.old. The built-in list covers roughly half of this article's categories with zero risk.
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