The invisible passengers: hidden files macOS puts on every external drive
You plug in a USB drive or SD card, copy a few files, and eject it. Simple enough. But macOS has quietly created several hidden files on that drive — and if you've been using it for years, those invisible files can add up to gigabytes.
What hidden files does macOS create?
| File / Folder | What it is | Typical size |
|---|---|---|
.Trashes | Trash for that drive — files you "deleted" but didn't empty | 0 – many GB |
.Spotlight-V100 | Spotlight search index for the drive's contents | 100 MB – 2 GB |
.fseventsd | File system event log (used by Time Machine and Spotlight) | 10 – 500 MB |
.DS_Store | Folder display preferences (icon positions, view mode) | A few KB per folder |
._* files | Resource forks for files — metadata macOS uses on non-Mac file systems | A few KB each |
How to see hidden files
In Finder, open the external drive and press Cmd + Shift + . (period). Hidden files and folders appear dimmed. Press the same shortcut again to hide them.
You can also use Terminal:
ls -la /Volumes/YourDriveName/
This shows everything, including dot-files that Finder normally hides.
Cleaning up: what's safe to remove
.Trashes — the biggest win
When you delete a file from an external drive, macOS moves it to a .Trashes folder on that drive instead of your main Trash. These files don't disappear until you empty the Trash while the drive is connected.
To clean: connect the drive, open Trash in the Dock, and look for items from the external drive. Empty Trash to permanently delete them.
.Spotlight-V100 — safe to delete
This is the Spotlight search index for the drive. Deleting it is harmless — macOS rebuilds it next time the drive is connected (and indexed). If you don't need to search the drive's contents from Spotlight, you can even prevent re-indexing:
- Open System Settings → Spotlight (or Siri & Spotlight).
- Under Privacy, add the external drive to the exclusion list.
.fseventsd — safe to delete
File system event logs used by Time Machine and Spotlight. Removing them is safe — they're recreated as needed. On drives that have been connected for years, this folder can grow to several hundred megabytes.
.DS_Store files — safe but persistent
Each folder on the drive gets a .DS_Store file that stores Finder's display preferences (icon size, view mode, position). They're tiny individually but can be annoying if you share the drive with Windows or Linux users who see them as clutter.
You can delete them, but macOS recreates them whenever you open a folder in Finder. They're harmless — treat them as a cosmetic nuisance rather than a storage problem.
._ (dot-underscore) files — safe to delete
These appear on drives formatted as FAT32 or ExFAT (common for drives shared between Mac and Windows). They store Mac-specific metadata that the file system doesn't natively support. Deleting them is safe — you might lose custom Finder tags or icon previews, but the actual files are unaffected.
What not to do
- Don't delete files you don't recognize without checking. Some hidden files belong to apps that use the drive (backup software, media tools). If it's not one of the dot-files listed above, leave it alone or look it up first.
- Don't reformat the drive just to clean up. Reformatting erases everything — hidden files and your actual data. It's the nuclear option for a problem that needs a broom.
If your main Mac disk is also running low, the hidden files on external drives are just part of the picture. Check our guide to finding what's eating your space for a full walkthrough.
External drives get cluttered. So does your Mac.
Gigatidy cleans the caches, logs, and leftovers that pile up on your startup disk — the stuff that's even harder to find than .Trashes on a USB stick.
Meet Gigatidy →FAQ
Why does my external drive show less free space than expected?
The most common reason is the .Trashes folder: files you deleted from the drive are still sitting in its hidden Trash. Connect the drive, empty the Trash, and check the free space again. Spotlight indexes and file system logs also contribute.
Can I prevent macOS from creating hidden files on my external drive?
Not entirely — .DS_Store files and resource forks are created automatically when you browse the drive in Finder. You can prevent Spotlight indexing by adding the drive to the Spotlight Privacy list, which stops .Spotlight-V100 from being created.
Are these hidden files visible on Windows?
Yes, if "Show hidden files" is enabled on Windows. The .DS_Store, ._ files, and .Trashes folder will appear. They're harmless on Windows but can be confusing. Deleting them on Windows is safe — macOS will recreate them next time.