How to reduce or shrink a partition in windows 10?

There are several reasons why you can't shrink a partition in Windows 10, even if it looks like there is free space. Here's a breakdown of the most common causes.

1. Unmovable Files Are Blocking the Shrink

Some system files like the page file, hibernation file, or shadow copies—are marked as unmovable and located at the end of the volume. These block the shrinking operation because Windows can only shrink from the "end" of a volume.

You need to turn off system protection:

Go to Control Panel > System > System Protection > Configure and turn it off for the drive.

2. Insufficient Continuous Free Space

Even if you have 100 GB free, that space might be fragmented, and diskpart or Disk Management can't use non-contiguous space for shrinking.

To fix this, please run Disk Defragmenter (dfrgui) to consolidate free space.

3. Volume Is Not NTFS

Shrinking is only supported on NTFS partitions. If the volume is FAT32 or another file system, shrinking won’t be available.

Please convert the file system to NTFS with this commnad:

convert D: /fs:ntfs

Once it is fixed, you can now reduce the size of volume in Windows 10. or Windows 11.