About reparse points

Reparse points are file system objects used to extend the attributes of a file system. Not all file systems support reparse points; for example, NTFS and ReFS support them, but the FAT file system does not. A reparse point consists of:

• User-defined data
• A reparse point tag that uniquely identifies the file system filter driver that owns the reparse point. All reparse point tags are assigned by Microsoft and are defined in ntifs.h. Some tags are reserved for Microsoft; non-Microsoft tags can be requested.

A filter can set or delete a reparse point on a file or directory by calling FltTagFileEx and FltUntagFile.

When a file system opens a file with a reparse point, it attempts to find the file system filter associated with the data format identified by the reparse tag. If present, the associated filter should process the file as directed by the reparse data.

For more information about reparse points, see the Windows SDK documentation.