What the system-files mode unlocks
The regular window of Disk Cleanup shows only user-level items: thumbnails, temporary files, the Recycle Bin. Everything that actually accumulates over years — superseded update components, upgrade logs, crash dumps — is hidden behind the “Clean up system files” button. Click it, pick drive C: again, and the second scan lists up to a dozen system categories with honest size estimates.
On most installations, four or five of these categories deliver the bulk of the space. It is safe to check them all, because every item describes data Windows can rebuild or no longer needs. The one exception is described below.
- Windows Update Cleanup — superseded update components in the component store, usually the biggest item
- Previous Windows installation(s) — the Windows.old folder after a feature update
- Delivery Optimization Files — update fragments cached for sharing with other PCs
- Windows Error Reporting and system memory dumps — the traces of crashes
- Thumbnails — Windows rebuilds them the next time you open folders
- DirectX Shader Cache — rebuilt by games and GPU drivers
Step by step: a deep clean of drive C:
Press Win+R, type cleanmgr and press Enter; select drive C: in the dialog. When the first window with checkboxes appears, do not click OK yet — click “Clean up system files” in the bottom left. Disk Cleanup restarts, asks for the drive again and then shows the full category list. Check the big items from the list above, review the sizes in the description pane, and click OK → “Delete Files”. A full pass over the component store can run ten to twenty minutes; Windows may seem busy — let it finish.
Two checkboxes deserve a second look. “Downloads” deletes the entire contents of your Downloads folder — leave it unchecked unless you truly mean it. “Windows ESD installation files” contains the recovery image used by “Reset this PC”: deleting it saves a couple of gigabytes, but any future reset will need internet or installation media. Everything else on the list is fair game.
Scripted cleanup, Storage Sense and what Disk Cleanup won't do
For repeated runs there is a scripted variant. cleanmgr /sageset:1 opens a settings dialog where you pick the categories once, and cleanmgr /sagerun:1 later executes exactly that selection without questions — handy for a quarterly maintenance routine. In Windows 11, Settings > System > Storage covers most of the same ground through Storage Sense and the Temporary files view, while Disk Cleanup still ships as a legacy tool.
The limits are worth knowing. Disk Cleanup never touches browser caches or leftovers of third-party apps, and it gives you no file-level preview — you trust the category descriptions. A weekly or monthly routine is where dedicated cleaners earn their place: Kleaner PRO bundles update leftovers, temp files and browser caches into one scheduled pass with a full preview of what will be removed.
Questions and Answers
Is Disk Cleanup safe to use in Windows 10?
Yes. Every category describes data Windows can rebuild — temporary files, caches, old update components; the only risky checkboxes are Downloads and Windows ESD installation files.
How long does Windows Update Cleanup take?
Typically ten to twenty minutes, depending on the component store size and drive speed. The progress bar may sit still for a while — that is normal.
Why don't I see the system categories in the list?
They appear after clicking “Clean up system files”, or immediately if you launch cleanmgr from an elevated command prompt. If the button is missing, your account probably lacks administrator rights.
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