Fixes / Windows · Checked

Windows "Low Disk Space" on Local Disk (C:): what it means and fixes

Short answer

Windows shows this warning when your C: drive, where Windows and most apps live, is almost full. Updates, apps and even saving files can fail at that point. The fastest fix is Disk Cleanup: type "disk cleanup" in the taskbar search, choose C:, select "Clean up system files", tick Temporary files, Windows Update Cleanup and Recycle Bin, then click OK and Delete Files.

What this message means

Local Disk (C:) is the drive Windows is installed on. When its free space gets very low, Windows shows this notification because it needs working room for updates, temporary files, virtual memory (pagefile.sys) and app caches. The warning does not mean the drive is failing. It only means the drive is nearly full. If you ignore it, Windows Update may fail, apps may crash or refuse to save, and the PC can slow down. Freeing even 10 to 20 GB is usually enough to stop the warning and let Windows run normally again. The Storage page in Settings shows what is taking up the space.

Common causes

CauseHow to tell
Temporary files and leftover Windows Update filesIn Settings > System > Storage, "Temporary files" shows several GB. Disk Cleanup lists large amounts under "Windows Update Cleanup" or "Temporary files" after you click "Clean up system files".
A previous Windows installation (Windows.old) after a major upgradeA folder named Windows.old sits at the root of C:, and Disk Cleanup shows "Previous Windows installation(s)", often 10 GB or more. This usually starts right after a feature update.
Large apps and games installed on C:The Installed apps list (Windows 11) or Apps & features (Windows 10), sorted by size, shows games or programs using tens of GB each.
Personal files piling up in Downloads, Desktop, Videos or PicturesStorage in Settings shows "Documents", "Pictures", "Videos" or "Other" as the largest category, and the Downloads folder holds old installers, ZIP files or videos.
Hidden system files: the hibernation file, restore points or a large pagefileC: is full even though your folders look small. hiberfil.sys is about as large as your installed RAM, and System Protection can hold several GB of restore points. "System & reserved" in Storage shows a large number.
A small SSD, which is common on laptops with 128 GB or 256 GB drivesRight-click C: in File Explorer and choose Properties. A total capacity of about 118 GB or 237 GB fills up quickly with Windows, updates and a few apps.

How to fix it

1. Run Disk Cleanup with system files included

  1. Type "disk cleanup" in the taskbar search box and open Disk Cleanup.
  2. Select drive C: and click OK.
  3. Click "Clean up system files" and select C: again when asked.
  4. Tick Windows Update Cleanup, Temporary files, Delivery Optimization Files, Recycle Bin and, if listed, Previous Windows installation(s). Leave Downloads unticked unless you have checked that folder.
  5. Click OK, then Delete Files. Removing Windows.old means you can no longer roll back to the previous Windows version.

2. Use Cleanup recommendations and Temporary files in Settings

Windows 11 (Cleanup recommendations). On Windows 10, use Settings > System > Storage > Temporary files, or "Free up space now".

  1. Open Start > Settings > System > Storage.
  2. Select "Cleanup recommendations" and look through Temporary files, Large or unused files, Files synced to the cloud and Unused apps.
  3. Tick the items you do not need and click "Clean up" in each section.
  4. Back on the Storage page, open "Temporary files", tick the categories you want to remove and click "Remove files".

3. Uninstall large apps and games you do not use

Windows 11: Settings > Apps > Installed apps. Windows 10: Settings > Apps > Apps & features.

  1. Open Settings > Apps > Installed apps (Windows 11) or Settings > Apps > Apps & features (Windows 10).
  2. Set "Sort by" to Size (large to small).
  3. On Windows 11, click the three dots (...) next to an unused app and choose Uninstall. On Windows 10, click the app, then Uninstall.
  4. Confirm and follow the uninstaller. Game launchers such as Steam or Epic can also move games to another drive instead of removing them.

4. Turn on Storage Sense so it does not happen again

  1. Open Start > Settings > System > Storage.
  2. Turn Storage Sense On.
  3. Select Storage Sense and choose how often it runs, how long Recycle Bin items are kept, and when unopened Downloads files are removed.
  4. If you use OneDrive, set when unused cloud files become online-only. This keeps them in OneDrive but frees space on C:.
  5. Click "Run Storage Sense now" to clean up immediately.

5. Move personal files and change where new files are saved

Windows 11: Settings > System > Storage > Advanced storage settings > Where new content is saved. Windows 10: Settings > System > Storage > Change where new content is saved.

  1. Plug in an external drive or use a second internal drive (D: or similar).
  2. In File Explorer, select large folders or files from Videos, Pictures, Downloads or Desktop, click Cut, open the other drive and click Paste.
  3. Open Settings > System > Storage, then "Where new content is saved" (under Advanced storage settings on Windows 11).
  4. Point new apps, documents, music, photos and videos to the other drive and click Apply for each.

6. Reclaim space used by hibernation and restore points

Needs an administrator account. Turning off hibernation also disables Hibernate and hybrid sleep.

  1. Search for cmd, right-click Command Prompt and choose Run as administrator.
  2. Type powercfg.exe /hibernate off and press Enter. This deletes hiberfil.sys, which is about the size of your RAM. To undo it later, run powercfg.exe /hibernate on.
  3. For restore points, search for "Create a restore point" and open it. Select Local Disk (C:) and click Configure.
  4. Lower the Max Usage slider (for example to 3 to 5 percent), or click Delete to remove old restore points, then click OK.

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Still not fixed?

If C: is still full, find out exactly what is using the space. Open Settings > System > Storage and click "Show more categories" to see the breakdown, or run a free disk-usage tool such as TreeSize Free or WinDirStat as administrator to list the largest folders. Common hidden culprits are app caches in C:\Users\<name>\AppData, old phone backups, virtual machine disks and runaway log files. Also run a full scan in Windows Security, because malware can fill a drive. If the drive is simply too small for how you use the PC, the lasting fix is a larger SSD or a second drive. A local repair shop or your PC maker's support can clone Windows onto a bigger drive.

Questions people ask

Why does my C drive keep filling up by itself?

Windows Update downloads, temporary files, app caches, restore points and OneDrive or browser caches grow in the background. Turning on Storage Sense deletes much of this automatically, and Disk Cleanup with "Clean up system files" removes old update files.

Is it safe to delete Windows.old and Windows Update Cleanup files?

Yes, if your current Windows version works properly. The only downside is that you can no longer roll back to the previous Windows version or uninstall some older updates. Windows removes Windows.old by itself after about 10 days anyway.

How much free space should C: have?

Keep at least 15 to 20 GB free so Windows feature updates can install and the pagefile and temporary files have room. On larger drives, around 10 to 15 percent free is a comfortable target.

Can I just turn off the Low Disk Space warning?

An administrator can set the DWORD value NoLowDiskSpaceChecks to 1 under HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer. This only hides the notification, though. A full C: drive still breaks updates and slows the PC, so free up space first.

Can I move space from D: to C: instead?

Only if D: is on the same physical disk and the unallocated space sits directly after C:. In that case, Disk Management (right-click Start > Disk Management) can use Extend Volume after D: has been backed up and deleted. Otherwise you need a third-party partition tool or a larger drive.

Sources

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