The Invisible Shrinking Act
Windows 11, when running on an NTFS-formatted drive, has the capability to transparently compress individual files and entire folders to reclaim disk space. This compression can be triggered automatically by certain system maintenance routines, Storage Sense policies, or even inherited folder attributes that silently propagate to every new file you create within a directory. The result is that files you save appear to take up less space on disk, but they require extra CPU cycles to decompress every time they are read, leading to noticeable performance degradation when working with large video projects, databases, or virtual machine disk images that are constantly being accessed.
Disabling Automatic NTFS Compression
To stop Windows 11 from automatically compressing files on your NTFS drives, you need to remove the compression attribute from the affected directories and disable any Storage Sense rules that trigger it.
First, open File Explorer and navigate to the drive or folder where you have noticed files are being compressed (compressed files and folders appear in blue text by default). Right-click on the drive or folder and select Properties. On the General tab, click the Advanced… button. In the Advanced Attributes dialogue, you will see a checkbox labelled Compress contents to save disk space. Uncheck this box and click OK. When prompted, select Apply changes to this folder, subfolders and files to recursively decompress everything within. Next, to prevent Storage Sense from reintroducing compression, open Settings > System > Storage > Storage Sense. Review the cleanup schedules and ensure that no policy is configured to compress infrequently accessed content. If you need a system-wide guarantee, open an elevated Command Prompt and run compact /u /s:"C:\" /a to forcefully uncompress all files on the C: drive and remove inherited compression attributes.