Free Tool to Fix C Drive Is Filling Up in Windows 11

by John, Updated on: August 15, 2026

Just like in Windows 10, the C drive often gets full on Windows 11 computers. Many users report that the C drive is filling up in Windows 11 for no reason. What should you do in this situation—replace the disk with a larger one, or reinstall the operating system and all your programs? In most cases, you can solve this problem easily without buying a new disk or recreating partitions and reinstalling everything. This article explains why the C drive is filling up automatically on Windows 11/10 computers and how to solve this issue quickly and easily.

C drive filling up

Why Is C Drive Filling Up in Windows 11/10 Laptop/Desktop/Tablet

1. Program Installation

In the digital age, computers can perform countless tasks, requiring you to install various programs for work, daily life, study, and entertainment. All programs are installed to the C: drive by default. The more programs you install, the less free space is left on the C drive.

2. Program Output

When installing programs, there is usually an option to change the installation path, although few people actually do it. Some programs pop up a notification giving you the option to change the output path. However, most programs output files directly to the C drive by default without notifying you. Programs used for video editing, heavy projects, and gaming will produce many large files, which eat up free space on the C drive very quickly.

3. System Protection

On many Windows 11 computers, System Protection is enabled by default. Press the Windows and R keys, type "sysdm.cpl ,4", and press Enter to see if it is enabled on your computer. If it is enabled, you can undo system changes by reverting your computer to a previous restore point. This is a helpful feature, but it also consumes a massive amount of disk space. There could be multiple restore points stored, and each associated file is very large.

4. Large System-Required Files

Some system-required files are very large and are saved on the C drive by default, such as the paging file and the hibernation file. The paging file is used as virtual RAM and is often set to 2GB or more. The hibernation file is used to save the system status before the computer goes to sleep, and it also takes up significant space.

5. Junk Files

Many junk and temporary files are continuously generated on the C drive, such as temp files, cache, logs, and browser data. Individual files might not be large, but they can take up a massive amount of space in total.

How to Fix Windows 11/10 C Drive Filling Up Issue

To fix the C drive filling up issue on a Windows 11/10 computer, you might find many methods through a Google search. However, to solve this problem quickly and efficiently, you only need to focus on the 3 most effective methods below.

Method 1 - Clean Up C Drive

When the C drive is filling up on a Windows 11/10 laptop, desktop, or tablet, the first thing you should do is clean up the disk. Remove junk and unnecessary files from the C drive to reclaim disk space. Even if you cannot reclaim a large amount of free space, your system will continue running properly without throwing low disk space alerts constantly.

How to clean up the disk when the C drive is filling up in Windows 11/10:

  1. Press the Windows and R keys together, type cleanmgr, and press Enter.
  2. The C: drive is selected by default; simply click OK to continue.
  3. Check the boxes next to the junk files you want to remove, and click OK to continue.
  4. Confirm the deletion.
  5. Repeat from step 1, but click Clean up system files in step 3 to remove deeper system junk.

Method 2 - Move Programs and Files

Since Windows 10, you can move installed apps (downloaded from the Microsoft Store) out of the C drive without reinstalling them. Follow the steps below when system partition C is filling up:

  1. Right-click the Windows logo on the taskbar and select Settings > Apps > Apps & features.
  2. Click an app or game.
  3. Click the Move button.
  4. Select the new location from the drop-down list.
  5. Click the Move button again to confirm.
  6. Repeat step 2 to move more items.

To get more free space, you can follow additional methods to free up disk space in Windows 11 or Windows 10.

Method 3 - Move Free Space from Other Volumes

In general, you should keep at least 20GB of free space on the C drive. If you cannot reclaim plenty of free space using the methods above, you had better increase the C drive size. Otherwise, the C drive will become full again shortly. You can change partition size in Windows 11/10 with a safe tool to shrink a large partition and transfer the free space to the C drive.

Because resizing partitions carries inherent risks of system damage and data loss, it is highly recommended to back up your computer in advance and use safe partition software.

Compared to other tools, NIUBI Partition Editor provides advanced data protection technologies to secure your system and data. Furthermore, it has a free edition for Windows 11/10/8/7/Vista/XP home users with the following features.

Download and launch NIUBI Partition Editor Free Edition, then watch the video to see how to extend the C drive with free space from other volumes:

Windows 11

The operating system, programs, and everything else (except partition sizes) remain exactly the same as before. Besides reallocating partition sizes, this free disk partition software helps you perform many other disk partition management operations, such as moving, merging, converting, copying, defragging, erasing data, optimizing file systems, and scanning bad sectors.

Expand the C drive as large as possible and clean up the disk monthly to remove newly generated junk files. By doing this, you can fix the C drive filling up issue completely.

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