What is the .Spotlight-V100 folder on your drive?

You plug a USB stick or an external drive into a Windows PC, a TV or a camera, and there it is: a folder called .Spotlight-V100 that you never made. Sometimes it is tiny. Sometimes it is a few gigabytes. Either way, it is your Mac's doing.

It is the search index for that drive

When you connect a drive to a Mac, Spotlight reads everything on it and builds an index so the files show up when you search. It keeps that index on the drive itself, in a folder at the top level called .Spotlight-V100. The dot at the front makes it hidden on a Mac, which is why you only notice it when the drive visits another device.

It usually arrives with a few siblings made for the same reason: .fseventsd, which logs changes to the drive, and .Trashes, which holds files you deleted from it on a Mac. On drives formatted as exFAT or FAT32 you may also see small files starting with ._, which carry Mac-only details that those formats cannot store.

None of this is a virus or a sign that something is wrong. It is housekeeping.

Is it safe to delete?

Yes. Deleting .Spotlight-V100 does not touch any of your files. It only throws away the index. The catch is that the next time the drive is connected to a Mac, Spotlight notices the index is missing and builds a new one, so on its own, deleting it is a temporary fix.

If the folder is large, deleting it can also be a quick way to reclaim space on a small flash drive before handing it to someone. Just expect it back.

How to stop it being created for one drive

If you would rather a particular drive was never indexed, tell Spotlight to leave it alone:

• In System Settings. Open Spotlight settings, choose Search Privacy, and add the drive to the list. Spotlight stops indexing anything on it.
• In Terminal. mdutil -s /Volumes/DriveName shows whether indexing is on for a drive, and sudo mdutil -i off /Volumes/DriveName turns it off. Replace DriveName with the drive's name as it appears in Finder.
• To rebuild a broken index instead. sudo mdutil -E /Volumes/DriveName erases the index and starts again, which is the usual fix when Spotlight stops finding files on a drive it used to search fine.

There is a trade-off, and it is worth being clear about it. A drive that Spotlight does not index is a drive Spotlight cannot search. For a flash drive you use to move files to a printer, that is fine. For a drive full of work, it means giving up search on it entirely.

The index lives on the drive. So when the drive is in a drawer, so is the index.

The bigger problem hiding in that folder

Where Spotlight keeps this index explains the most frustrating thing about external drives on a Mac. Because the index is on the drive, ejecting the drive takes its index with it. The moment you unplug it, every file on it drops out of search, and there is no way to ask your Mac which of your drives has the file you need.

That is a sensible design for a disk that travels between Macs, and a poor one if you own several drives and keep most of them unplugged. We wrote more about that in how to find a file on a drive that is not plugged in.

Keep a copy of the map on your Mac

GetFerret takes the opposite approach. It catalogs each drive once and keeps that catalog on your Mac, so a drive's files stay searchable after you eject it. Press ⌥ Space, type part of a name, and files on unplugged drives come back alongside everything else, labelled with the drive they live on.

When a drive is unplugged, GetFerret asks where you are storing it, so later it can tell you which drawer to open, not just which drive. It does not need Spotlight's folder at all, so you are free to switch Spotlight off for drives you never want indexed, without losing the ability to search them.