What are fskitd and userfsd?

2023-03-14 17:00

You might see processes starting with filesystems. in Activity Monitor. These handle file system support on macOS.

What is fskitd?

fskitd is the FSKit daemon. FSKit is Apple's framework for running file system code outside the kernel. This follows Apple's push to move things out of the kernel for better stability and safety.

What is userfsd?

userfsd runs file system code that lives outside the kernel. When you mount a drive that uses a file system provided by an FSKit plug-in (rather than one built into the kernel), userfsd runs the code.

What file systems does macOS support?

macOS has built-in support for:

APFS: Apple File System (the default, runs in the kernel)
HFS+: the older Mac file system (runs in the kernel)
FAT/FAT32/exFAT: used by USB drives and SD cards (runs in the kernel)
NTFS: the Windows file system (read-only, runs in the kernel)

Extra file systems can be added through FSKit plug-ins or third-party tools.

When do these processes run?

fskitd and related processes run when you mount drives that use file systems provided by plug-ins. If you only use standard APFS and FAT drives, these processes stay quiet.

Should you worry?

No. They are normal macOS processes that let your Mac support more types of file systems.

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