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C drive full for no reason? Find what is using space and fix it

By the Brightfix team. Updated October 7, 2026. Applies to Windows 11 24H2, 25H2 and 26H2, Home and Pro. Most steps also work on Windows 10.

Quick answer

Open Settings > System > Storage and select Show more categories to see what is using the space. Usually it is temporary files, update leftovers, restore points, the hibernation file or Windows.old, and Windows has safe built-in tools to clear each one.

Before you start

  • Back up anything important first, especially if the drive is almost completely full.
  • Never delete files by hand inside C:\Windows, C:\Program Files or the page file. Use the built-in tools below.
  • Check the Downloads and Recycle Bin boxes carefully before you remove anything. They can hold files you still want.
  • Install all Windows updates first. A 2026 bug that filled some drives was fixed through Windows Update.

1See what is using the space

Look before you delete, so you clear the thing that is actually big.

  1. Open Settings > System > Storage.
  2. Wait for the bar for C: to finish loading and note the free space.
  3. Select Show more categories to see the full list.
  4. Select System & reserved. It lists system files, virtual memory (the page file), the hibernation file, System Restore and reserved storage.
  5. Go back and select Temporary files to see how much can be cleared.
  6. Select Other to see the largest folders Windows could not sort into a category.
What you should see

A list of categories with sizes. The biggest ones tell you which of the steps below will help most.

If it did not work: If the Storage page stays blank, restart the PC and open it again. It can take a minute on a very full drive.

Undo: Nothing to undo. This only looks.

2Clear temporary files in Settings

Temporary files, update leftovers and Delivery Optimization files are safe to remove and are often the biggest quick win.

  1. Open Settings > System > Storage > Temporary files.
  2. Read each checkbox. Good ones to tick: Temporary files, Delivery Optimization Files, Windows Update Cleanup, Thumbnails.
  3. Leave Downloads unticked unless you have checked that folder yourself.
  4. Tick Recycle Bin only after opening it and making sure nothing in it is needed.
  5. Leave Previous Windows installation(s) unticked unless you are sure you will not go back to the old version.
  6. Select Remove files.
What you should see

The Temporary files total drops and free space on C goes up.

If it did not work: If very little space came back, move on to Disk Cleanup and the component store steps below.

Undo: Temporary files cannot be restored, but Windows recreates what it needs. Items removed from the Recycle Bin are gone for good.

3Turn on Storage Sense and free up OneDrive space

Storage Sense keeps temp files and the Recycle Bin from building up again, and OneDrive can keep files online only.

  1. Open Settings > System > Storage and turn on Storage Sense.
  2. Select Storage Sense to open its options. Set how long items stay in the Recycle Bin.
  3. Leave the Downloads option set to Never if you keep files there.
  4. Select Run Storage Sense now.
  5. If you use OneDrive, open File Explorer, right-click a large OneDrive folder you do not need offline, and choose Free up space.
What you should see

Storage Sense shows how much it cleaned. OneDrive files you freed show a cloud icon and still open when you are online.

If it did not work: If OneDrive does not show Free up space, open OneDrive settings and turn on Files On-Demand.

Undo: Turn Storage Sense off in the same place. In OneDrive, right-click a folder and choose Always keep on this device to download it again.

4Run Disk Cleanup for system files

Disk Cleanup's system mode finds update leftovers and error reports that need administrator rights to remove.

  1. Press Start, type Disk Cleanup, and open it.
  2. Choose drive C: and select OK.
  3. Select Clean up system files and choose C: again if asked.
  4. Tick Windows Update Cleanup, Delivery Optimization Files, Temporary files and Windows error reports if listed.
  5. Leave Previous Windows installation(s) unticked unless you are done with the old version.
  6. Select OK, then Delete Files.
What you should see

Disk Cleanup works for a few minutes and closes. Free space on C goes up.

If it did not work: If Windows Update Cleanup does not shrink, the component store cleanup in the next step can help.

Undo: These files cannot be restored, but Windows does not need them to run.

5Clean up the component store with DISM

The WinSxS folder keeps old versions of updated Windows files, and Windows' own cleanup can remove the ones no longer needed.

  1. Press Start, type cmd, right-click Command Prompt, and choose Run as administrator.
  2. Type DISM /Online /Cleanup-Image /StartComponentCleanup and press Enter.
  3. Wait for it to reach 100 percent. It can take 10 to 30 minutes and may pause for a while.
  4. Close the window and check free space in Settings again.
What you should see

DISM says the operation completed successfully.

If it did not work: If DISM shows an error, run DISM /Online /Cleanup-Image /RestoreHealth first, then try again.

Undo: Nothing to undo. Windows normally runs this cleanup by itself on a schedule. We do not suggest adding /ResetBase, because it stops you from uninstalling updates that are already installed.

6Optional: limit restore point space or turn off hibernation

Restore points and the hibernation file can take many gigabytes, but both are useful, so treat these as trade-offs.

  1. Restore points: press Start, type Create a restore point, and open it.
  2. Select drive C: and choose Configure.
  3. Leave Turn on system protection selected. Move the Max Usage slider lower (for example, 5 percent), then select Apply. Older restore points are removed when the limit is reached.
  4. Hibernation (optional): only do this if you never use Hibernate. Open Command Prompt as administrator.
  5. Type powercfg /hibernate off and press Enter. This deletes the hibernation file, but it also turns off Hibernate, hybrid sleep and Fast Startup.
What you should see

System & reserved in Storage settings gets smaller. After the powercfg command, Hibernate disappears from the power menu.

If it did not work: If the Configure button is greyed out, System Protection is managed by your organization. Do not turn system protection off to save space.

Undo: Move the Max Usage slider back up. To bring hibernation back, run powercfg /hibernate on as administrator.

ItemWhereSafe to delete by hand?Safe way instead
System32 and other Windows filesC:\WindowsNo. Windows can stop starting.None needed
Component storeC:\Windows\WinSxSNo. It can break updates and startup.DISM StartComponentCleanup or Disk Cleanup
Page fileC:\pagefile.sysNo. Windows manages it.Leave it to Windows
Hibernation fileC:\hiberfil.sysNo.powercfg /hibernate off (turns off Hibernate and Fast Startup)
Installed programsC:\Program FilesNo. Apps break and leave leftovers.Settings > Apps > Installed apps > Uninstall
Previous WindowsC:\Windows.oldNo. Permissions block it.Settings > Storage > Temporary files
Temporary filesTemp foldersYes, but Settings is easier.Settings > Storage > Temporary files

Why this happens

Windows keeps several large files and folders on C that do not show up as your own files. The hibernation file can be close to the size of your RAM, and the page file is used as extra memory. System Restore keeps snapshots, Windows Update leaves old files in the component store (WinSxS) and the update cache, and Delivery Optimization keeps update pieces to share. A full upgrade adds Windows.old. Settings groups most of this under System & reserved, which is why the drive looks full for no reason. In 2026, a bug also made a privacy database file (CapabilityAccessManager.db-wal) grow very large on some PCs. Microsoft improved this starting with the June 23, 2026 optional update (KB5095093).

Still stuck?

Why is System & reserved so big?

It includes the page file, the hibernation file, System Restore snapshots, reserved storage for updates and Windows itself. On a PC with lots of RAM, the hibernation and page files alone can be large. Restore points can also grow over time. Check each part in Settings > System > Storage > Show more categories > System & reserved.

Is it safe to delete the WinSxS folder?

No. Microsoft warns that deleting files from WinSxS by hand can stop Windows from starting and block updates. Use DISM with StartComponentCleanup, or Disk Cleanup with Windows Update Cleanup, which remove only the old versions Windows no longer needs.

Should I turn off System Restore to save space?

We do not suggest it. Restore points let you undo a bad update or driver. Lowering the Max Usage slider is a better middle ground, because Windows keeps recent restore points and removes the oldest ones when it reaches the limit.

Does turning off hibernation have downsides?

Yes. Running powercfg /hibernate off deletes the hibernation file, but it also turns off Hibernate, hybrid sleep and Fast Startup. Laptops that rely on Hibernate to save battery overnight lose that option. You can turn it back on with powercfg /hibernate on.

Was the 2026 storage bug fixed?

Microsoft's June 23, 2026 optional update (KB5095093) improved disk space use for the CapabilityAccessManager.db-wal file, and later monthly updates include that change. Install all current updates. If System & reserved is still huge after that, ask for help before deleting anything in ProgramData.

Will cleaning my C drive delete my documents or photos?

Not with the steps here, as long as you leave Downloads and Recycle Bin unticked unless you have checked them. Temporary files, update leftovers and restore points do not include your Documents, Desktop or Pictures folders.

Related guides

How we checked this guide

Steps checked against Microsoft Support and Microsoft Learn documentation on October 7, 2026. Not yet tested by us on a full drive. Screenshots coming soon.

Changes

  • October 7, 2026: First published.

Sources

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