# Why Is My C Drive Full? What Is Safe to Delete

> What fills the C drive on Windows 10 and 11, where each part lives, which are safe to remove, and the built-in tools and commands that remove them properly.

Canonical: https://bytesweep.app/answers/why-is-my-c-drive-full.html
Last updated: 2026-11-04

## Why is my C drive full, and what can I delete?

What fills the C drive on Windows 10 and 11, where each part lives, which are safe to remove, and the built-in tools and commands that remove them properly.

- By [Shajeen Ahamed](https://bytesweep.app/about.html#author)
- Updated 4 November 2026
- Steps checked against Microsoft's documentation

**Short answer**

Usually not your own files. Windows Update leftovers, a previous Windows installation (Windows.old), the hibernation and page files, temporary files, restore points, app caches and the Recycle Bin all sit on C:. Start in Settings, System, Storage, Cleanup recommendations, then use a folder-size tool for whatever the categories do not explain.

### Where does Windows show what is using the space?

On Windows 11, open Start, Settings, System, Storage. The page splits the drive into categories (Apps, Temporary files, System & reserved, Other); **Show more categories**lists the rest.**Cleanup recommendations**, on the same page, offers temporary files, large or unused files, files already synced to the cloud and unused apps in one place.

On Windows 10, search the taskbar for Disk Cleanup, pick C:, then click **Clean up system files** to add Windows Update Cleanup, Delivery Optimization Files and, for ten days after an upgrade, Previous Windows installation(s). Microsoft's own steps for both versions are in [Free up drive space in Windows](https://support.microsoft.com/en-us/windows/free-up-drive-space-in-windows-85529ccb-c365-490d-b548-831022bc9b32).

**Storage Sense** (Settings, System, Storage) can do the routine part on a schedule: temporary files, the Recycle Bin after a number of days, and cloud files you have not opened in a while.

### What usually fills the C drive?

| What | Where | Safe to remove? | How |
| --- | --- | --- | --- |
| Windows Update downloads | `C:\Windows\SoftwareDistribution\Download` | Yes, once updates are installed | Cleanup recommendations or Disk Cleanup, Windows Update Cleanup |
| Delivery Optimization files | A system cache of update pieces shared with other PCs | Yes | Disk Cleanup, Delivery Optimization Files |
| Previous Windows installation | `C:\Windows.old` | Yes, if you will not roll back | Listed in cleanup for 10 days after an upgrade; removing it removes the way back |
| Component store | `C:\Windows\WinSxS` | Never by hand | DISM. See [is it safe to delete WinSxS](https://bytesweep.app/answers/is-it-safe-to-delete-winsxs.html) |
| Hibernation file | `C:\hiberfil.sys` | Only by turning hibernation off | `powercfg /hibernate off`. See [hiberfil.sys and pagefile.sys](https://bytesweep.app/answers/hiberfil-sys-pagefile-sys.html) |
| Page file | `C:\pagefile.sys` | No | Leave it system-managed, or move it to another drive |
| Temporary files | `%TEMP%`, `C:\Windows\Temp` | Yes, apart from files in use | Cleanup recommendations, Temporary files |
| Restore points | System Volume Information (hidden, protected) | Older ones, yes | System Properties, System Protection, Configure: lower Max Usage or Delete |
| Crash dumps | `C:\Windows\MEMORY.DMP`, `C:\Windows\Minidump` | Yes, unless someone is debugging | Disk Cleanup, System error memory dump files |
| Recycle Bin | `C:\$Recycle.Bin` | Yes, once you have checked it | Empty it; Storage Sense can do it on a schedule |
| OneDrive files kept locally | Your OneDrive folder | The local copy, yes | Right-click, Free up space (Files On-Demand). The file stays in OneDrive |
| WSL and Docker disks | `ext4.vhdx` under `%LOCALAPPDATA%\Packages`; Docker Desktop's under `%LOCALAPPDATA%\Docker` | Not by deleting | Delete data inside Linux or Docker, then compact the .vhdx |

### How do I check the size of the hidden system files?

hiberfil.sys, pagefile.sys and swapfile.sys are hidden and protected, so File Explorer does not show them by default. In a Command Prompt, `/a` lists them anyway:

```
dir C:\ /a
```

Restore points do not appear as files at all. This shows how much space they are using and how much they are allowed to use:

```
vssadmin list shadowstorage
```

Run it in a Command Prompt opened as administrator.

### How do I find which folders are biggest?

Windows has no folder-size column, so this PowerShell, run as administrator, adds up each folder at the top of C: and sorts them. It reads every file, so give it a few minutes:

```
Get-ChildItem C:\ -Directory -Force -ErrorAction SilentlyContinue | ForEach-Object {
  $bytes = (Get-ChildItem $_.FullName -Recurse -File -Force -ErrorAction SilentlyContinue |
            Measure-Object Length -Sum).Sum
  [pscustomobject]@{ Folder = $_.FullName; GB = [math]::Round($bytes / 1GB, 1) }
} | Sort-Object GB -Descending
```

Change `C:\` to `$env:USERPROFILE` to look inside your own folder, where downloads, videos, game libraries and AppData caches usually are. The free folder-size tools (WizTree, WinDirStat, TreeSize Free) do the same with a treemap and much faster; [how they compare](https://bytesweep.app/alternatives/) is on our alternatives pages.

### What should I not delete to get space back?

- Anything inside `C:\Windows\WinSxS`, `C:\Windows\Installer` or `C:\Windows\System32`. Windows will stop updating, or stop starting.
- `pagefile.sys`, by switching the page file off. It backs crash dumps and the memory commit limit; apps can fail with out-of-memory errors without it.
- `C:\ProgramData` as a whole. It holds app licences, databases and settings for every user.
- Folders under `AppData\Roaming` for apps you still use. That is their data, not cache.

### Can Bytesweep for Windows do this for me?

Bytesweep for Windows (Windows 10 and 11, from the Microsoft Store) measures each of the parts above and says what it is: Windows Update leftovers, the Delivery Optimization cache, the component store, Windows.old and upgrade files, crash dumps, temp files and thumbnails, browser caches, game launcher leftovers and old developer folders. Its storage analyzer shows any drive as an overview, a treemap, a sunburst, file types and folders, and a right-click in Explorer analyzes any folder.

What it cleans can be put back for 7 days, with exceptions it names before you confirm: the Recycle Bin, component store cleanup (which runs through DISM, never by deleting files) and vendor uninstallers cannot be undone. It is free to try for 3 days; cleaning needs a licence, $29.99 once per computer.

### Sources

Read on 4 November 2026. If something here has changed, write to [support@bytesweep.app](mailto:support@bytesweep.app) and it will be corrected.

- [Microsoft Support, Free up drive space in Windows](https://support.microsoft.com/en-us/windows/free-up-drive-space-in-windows-85529ccb-c365-490d-b548-831022bc9b32)
- [Microsoft Learn, Clean up the WinSxS folder](https://learn.microsoft.com/en-us/windows-hardware/manufacture/desktop/clean-up-the-winsxs-folder)
- [Microsoft Learn, Introduction to the page file](https://learn.microsoft.com/en-us/troubleshoot/windows-client/performance/introduction-to-the-page-file)

### Keep reading

- [**Is it safe to delete the WinSxS folder?**](https://bytesweep.app/answers/is-it-safe-to-delete-winsxs.html)
- [**Can I delete hiberfil.sys and pagefile.sys?**](https://bytesweep.app/answers/hiberfil-sys-pagefile-sys.html)
- [**Bytesweep for Windows**](https://bytesweep.app/windows.html)
- [**All answers**](https://bytesweep.app/answers/)

### See what is filling your disk, and why.

Bytesweep is free to try for 3 days on [Mac](https://bytesweep.app/mac.html), [Windows](https://bytesweep.app/windows.html) and [Linux](https://bytesweep.app/linux.html). Cleaning needs a licence: $29.99 once per computer, no subscription.

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