In the latest builds of Windows 10, there is a new feature, in Beta, called Windows Projected File System. I cannot find any information on Google, other than programming APIs that do not make sense to me.

What is it, and what kind of users would it be targeted for?

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2 Answers 2


Projected File System aka ProjFS is a feature similar to FUSE found on Linux (or to Dokan & WinFSP). It allows apps to create virtual file systems which appear indistinguishable from local folders, but their entire contents are generated "live" by the program. (In other words, you're seeing projections of files which might not be there.)

The primary use of ProjFS is Microsoft's "Git Virtual File System", an addon to the Git version management tool aimed at increasing its performance and reducing disk space usage when dealing with massive repositories. (Git was built for repositories containing just tens of thousands of files, such as Linux.git; but Microsoft have started using it internally for the Windows source repository, which is several orders of magnitude larger.)

Additionally, Visual Studio (Enterprise)'s "Live Unit Testing" feature requires ProjFS to be enabled

Currently ProjFS doesn't seem to be publicly documented, but I expect that sooner or later third-party developers will figure out how to use it as a FUSE alternative for implementing such virtual filesystems as sshfs, ftpfs, and so on.

Note: Projected File System has nothing to do with Windows File Protection.

As noted in the comments, documentation is now available for the feature.


Windows Projected File System is not an alternative to FUSE or Dokan.

It appears to be similar to FUSE and Dokan at first glance, even using callbacks to populate the file list, and read data from files.

However, once you read a file, the projected file is replaced with a physical file on your hard disk, which will stay on the disk.

  • So it's never again updated from the backing store? Is that what you're saying? Could you please name your sources for that. Apr 12, 2022 at 10:48
  • I didn't check if it was 'ever checking the backing store again', I just didn't want something that was writing files to the disk.
    – Dwedit
    Apr 12, 2022 at 19:31

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