Your C: drive is showing red in File Explorer. Windows is throwing “Low Disk Space” warnings. You can’t install updates because there’s not enough room. But when you look through your files — Documents, Downloads, Pictures — nothing seems big enough to explain where all the space went.
That’s because the biggest space eaters on Windows 11 are hidden. They’re system files, cached updates, leftover installation data, and background processes that quietly accumulate gigabytes over months of normal use. You never created these files, and Windows never asks you to clean them up.
I’m going to show you where these hidden space eaters are and how to safely reclaim the space — often 20 to 50 GB on a system that hasn’t been cleaned in a while.
Step 1: See What’s Actually Using Your Space
Before you start deleting things, find out where the space is going.
Settings → System → Storage
Wait for the scan to complete. Windows will show you a breakdown: Apps & features, Temporary files, System & reserved, Other, and more. Click “Show more categories” to see the full picture.
This overview tells you immediately where the biggest chunks of space are hiding. On most systems that haven’t been cleaned, you’ll see Temporary files eating anywhere from 5 to 30 GB.
Step 2: Enable and Run Storage Sense
Storage Sense is Windows 11’s built-in automatic cleaner. It runs in the background and removes files you don’t need — but it’s turned off by default on most systems.
Settings → System → Storage → Storage Sense
Turn it ON, then click “Configure Storage Sense or run it now” to set it up properly:
Run Storage Sense: Set to “During low free disk space” or “Every week” for regular cleaning.
Temporary files: Enable “Delete temporary files that my apps aren’t using.”
Recycle Bin: Set to “Delete files in my recycle bin if they have been there for over 30 days.” Nobody needs six months of deleted files.
Downloads folder: Set to “Delete files in my Downloads folder if they have been there for over 30 days.” This one is aggressive — check your Downloads folder first and move anything important before enabling it.
After configuring, click “Clean now” at the bottom to run it immediately.
Storage Sense typically frees 2-10 GB on its first run, depending on how long your system has been accumulating temporary files.
Step 3: Disk Cleanup with System Files (The Big One)
Storage Sense cleans user-level temporary files. But the really large space eaters — cached Windows updates, old installations, delivery optimization files — require Disk Cleanup with the system files option.
Start → type "Disk Cleanup" → select your C: drive → OK
Wait for the initial scan. When it finishes, you’ll see a list of file categories with sizes. But don’t start checking boxes yet — click “Clean up system files” at the bottom. This rescans with elevated permissions and reveals the really big items.
After the second scan, look for these categories:
Windows Update Cleanup — Old update files kept as backup. Usually 3-10 GB. Safe to delete. You won’t be able to roll back to older updates, but you almost never need to.
Previous Windows installations (Windows.old) — If you upgraded from Windows 10 or did a major update, this folder contains your entire previous installation. It can be 20 GB or more. If everything works fine on your current Windows version, delete it.
Delivery Optimization Files — Files used by Windows’ peer-to-peer update delivery system. Usually 1-5 GB. Safe to delete.
Temporary Windows installation files — Leftover data from the upgrade process. Sometimes 5-10 GB. Safe to delete.
Device driver packages — Old driver versions that Windows keeps as backup. Usually 1-3 GB. Safe to delete unless you frequently roll back drivers.
Check all of these, click OK, then Delete Files. On a system that’s never been cleaned, this single step can free 15-30 GB.
Step 4: Kill the Hibernation File
This is the hidden space eater that shocks people the most.
Windows maintains a file called hiberfil.sys in your C: drive root. You can’t see it in File Explorer because it’s a protected system file. Its size equals your RAM — if you have 16 GB of RAM, the hibernation file uses 16 GB of disk space. 32 GB of RAM? That’s a 32 GB file sitting on your drive.
The hibernation file stores the contents of your RAM when you put your computer into hibernation (not sleep — hibernation is different). When you wake the computer, Windows reads the file back into RAM and restores your session.
If you never use hibernation (most laptop users use Sleep, not Hibernate), you can safely delete this file and reclaim all that space:
Open Command Prompt as Administrator
Type: powercfg /h off
Press Enter
The hibernation file is deleted immediately. You just reclaimed 8-32 GB depending on your RAM.
If you use hibernation but want to save some space:
powercfg /h /type reduced
This shrinks the hibernation file to about 40% of your RAM size. You can still hibernate, but Windows compresses the data more aggressively. On a 16 GB RAM system, this reduces the file from 16 GB to about 6.4 GB — saving nearly 10 GB.
Step 5: Clean Up the WinSxS Folder (Safely)
The WinSxS folder (C:\Windows\WinSxS) is Windows’ component store. It looks massive — sometimes appearing as 10-15 GB in File Explorer. But don’t panic, and never manually delete files from this folder. Much of what File Explorer shows is actually hard links to files stored elsewhere, so the real size is smaller than it appears.
That said, WinSxS does accumulate unnecessary data over time. Clean it safely using the DISM command:
Open Command Prompt as Administrator
Type: Dism /Online /Cleanup-Image /StartComponentCleanup
Press Enter
This removes old versions of system components that are no longer needed. It can take several minutes to complete. On a system with many accumulated updates, it typically frees 2-5 GB.
For an even more aggressive cleanup:
Dism /Online /Cleanup-Image /StartComponentCleanup /ResetBase
The /ResetBase option removes all superseded update versions permanently. This frees more space but means you can’t uninstall any previously installed updates. Only use this if your system is running stable and you’re confident you won’t need to roll back.
Step 6: Find and Remove Large Files You Forgot About
Sometimes the space is being used by files you created or downloaded and forgot about. Video files, ISO images, game installers, old backups — these can be massive.
The fastest way to find them:
Open File Explorer → click your C: drive → type size:gigantic in the search bar
This finds all files over 128 MB. Sort by size to see the biggest ones first. You’ll often find:
- Old ISO files from Windows or Linux installations (4-6 GB each)
- Video recordings from screen capture software
- Downloaded game or app installers you already installed
- Old system backup files (.bak, .vhd, .wim)
- Duplicate photo/video libraries
Don’t delete anything in the Windows or Program Files folders. Focus on your user folders — Downloads, Documents, Desktop, Videos.
Step 7: Move Large Apps and Games to Another Drive
If you have a second drive (or can add one), moving large applications frees significant space on your C: drive without losing access to them.
Move Windows Apps:
Settings → Apps → Installed apps → click the three dots next to an app → Move
Select your second drive. Not all apps support this, but many Windows Store apps do.
Move Steam games:
Steam → Library → right-click a game → Properties → Installed Files → Move Install Folder → select your other drive.
Move the Downloads folder:
Right-click the Downloads folder in File Explorer → Properties → Location tab → Move → select a folder on your other drive. All future downloads will automatically go to the new location.
Step 8: Set Up OneDrive Files On-Demand
If you use OneDrive, enable Files On-Demand to free space while keeping all your files accessible:
Right-click the OneDrive icon in the system tray → Settings → Sync and backup → Advanced Settings → Files On-Demand → ON
With Files On-Demand enabled, files you haven’t opened recently are stored only in the cloud. They appear in File Explorer with a cloud icon, and Windows downloads them only when you open them. This can free massive amounts of space if you have a large OneDrive library.
You can also right-click specific folders → “Free up space” to move them to cloud-only storage immediately.
Maintenance Schedule
To prevent your drive from filling up again:
Monthly: Run Disk Cleanup with system files option. Takes 2 minutes, typically frees 2-5 GB of accumulated update files.
After major Windows updates: Check for and delete the Windows.old folder. It appears after feature updates and takes 20+ GB.
Storage Sense: Leave it enabled with weekly cleaning. It handles temporary files and recycle bin automatically.
Quarterly: Search for large files (size:gigantic) and clean up anything you no longer need.
With these habits, you’ll never see that “Low Disk Space” warning again.