MacFUSE implements a mechanism that makes it possible to implement a fully functional file system in a user-space program on Mac OS X (10.4 and above). It aims to be API-compliant with the FUSE (File-system in USErspace) mechanism that originated on Linux. Therefore, many existing FUSE file systems become readily usable on Mac OS X. That said, MacFUSE has numerous user- and developer-visible interfaces that are specific to Mac OS X. The core of MacFUSE is in a dynamically loadable kernel extension.