C Drive Full? How to Free Up Space on Windows
A red bar under your C: drive in File Explorer is a warning sign. When the system drive runs out of space, Windows becomes slow, updates fail, and programs may crash. Luckily, most full drives are filled with files you do not need.
This guide shows you how to find what is using the space and clean it up safely.
See what is using space
Open Settings → System → Storage. Windows shows a breakdown of Apps, Temporary files, Documents, Pictures, Videos and more. Click Show more categories for the full list. Start with the largest category.
Delete temporary files
In Storage → Temporary files, Windows lists items like Windows Update cleanup, Delivery Optimization files, thumbnails and the Recycle Bin. Tick the boxes and click Remove files. After a major update, "Windows Update Cleanup" and "Previous Windows installation" can free 10 GB or more.
Turn on Storage Sense
On the Storage page, turn on Storage Sense. It automatically clears temporary files and can empty the Recycle Bin and old Downloads on a schedule you choose.
Uninstall large apps and games
Go to Settings → Apps → Installed apps and sort by Size. Games often take 50–100 GB each. Uninstall anything you no longer use.
Move personal files off C:
- If you have a second drive (D:), move large folders like Videos and Downloads there. Right-click the folder in File Explorer → Properties → Location → Move.
- Copy old videos and photos to an external drive.
- Use OneDrive's Files On-Demand, which keeps files in the cloud and downloads them only when opened.
Find hidden space hogs
- Hibernation file: if you never use hibernate, running
powercfg /hibernate offin an admin terminal removes a file that can be several GB. This also disables Fast Startup. - Old restore points: search for "Create a restore point" → Configure to limit how much space System Restore uses. Keep some space so restore still works.
- WhatsApp Desktop and browser caches can grow large over time.
Free tools like WinDirStat or WizTree show a visual map of what is taking space, making big forgotten files easy to spot.
How much free space do you need?
Aim to keep at least 15–20% of your C: drive free, and at least 20 GB for updates. If your drive is small, such as 128 GB, consider upgrading to a larger SSD; see our SSD upgrade guide.
Mistakes to avoid when cleaning your C: drive
When space is tight, it's tempting to delete anything that looks big. Some folders are essential to Windows, and deleting them can stop your PC from starting or break programs. Avoid these common mistakes:
- Don't delete folders in C:\Windows, C:\Program Files or C:\ProgramData manually. Uninstall programs properly through Settings instead.
- Don't delete the WinSxS folder. It looks huge, but much of its size is shared with other folders. Use Disk Cleanup's "Windows Update Cleanup" to reduce it safely.
- Don't use unknown "registry cleaner" or "PC optimizer" tools. They rarely free meaningful space and can cause problems.
- Don't delete the pagefile (pagefile.sys) unless you know what you're doing. Windows uses it when RAM runs out.
- Don't empty the Recycle Bin without checking it; people often find important files there.
Use Disk Cleanup for system files
The classic Disk Cleanup tool still works well. Search the Start menu for Disk Cleanup, choose drive C:, then click Clean up system files. Tick items such as Windows Update Cleanup, Temporary files and Delivery Optimization Files. It's safe and often frees several gigabytes.
Check user folders you forgot about
Your user folder (C:\Users\YourName) often holds forgotten space hogs: phone backups made by iTunes or the Apple Devices app, old video projects, virtual machines, and game recordings in Videos → Captures. Sorting these folders by size in File Explorer's Details view quickly reveals large files you no longer need.
Long-term fix
If you clean up regularly but the drive fills again within weeks, your drive is simply too small for how you use your PC. Moving personal files to a second drive or a larger SSD solves the problem for good.
Frequently asked questions
Can I delete the Windows.old folder?
Yes, using Storage → Temporary files → Previous Windows installation. You will lose the option to roll back to the previous version.
Is it safe to delete files in the Temp folder?
Yes, but use the built-in cleanup rather than deleting system folders manually.
Keep reading
How to Zip and Unzip Files on Windows (and Password-Protect Them)
Compress files into ZIP folders to save space and share easily, extract ZIP and RAR files, and add password protection.
Windows Update Stuck? How to Fix It Safely
What to do when Windows Update is stuck downloading, installing or on 'Working on updates', without risking your files.
Windows Security (Defender) Explained: Is It Enough?
A plain-language guide to Windows Security: what it protects, which settings to turn on, and how to run scans.