macFUSE

The kernel extension that lets third-party filesystems be implemented as ordinary programs.

What it does

macFUSE (formerly OSXFUSE) provides the FUSE API on macOS, so a filesystem can be written as a user-space process rather than a kernel driver. Things built on it include NTFS write support, SSHFS, S3 and cloud-storage mounts, and archive-as-filesystem tools.

It is a dependency rather than something used directly — ntfs-3g and similar tools need it present.

Notes

macFUSE installs a kernel extension, which on Apple Silicon requires reducing Startup Security to Reduced Security with third-party kernel extensions allowed, then a reboot. That is a real weakening of the machine’s security posture. Install it only if something you actually need depends on it, and prefer alternatives — Mounty for occasional NTFS writes, or a network share — where possible.

macOS’s FSKit framework is Apple’s supported replacement for this pattern, and newer filesystem implementations are moving to it.

Alternative to

Alternative	Type	Trade-off
FSKit	Built in	Apple’s supported, kernel-extension-free replacement; new filesystems are moving to it
A network share (SMB or NFS)	—	No driver, no security trade-off
Mountain Duck or ExpanDrive	Paid	Commercial cloud mounting that avoids the kernel extension