What to know about exFAT drives

Some external drives come formatted as exFAT, because Macs and Windows PCs can both read it. Storage Studio lets you use an exFAT drive, but marks it Compatibility: usable with warnings: exFAT can't hold some of the things a Mac stores alongside its files.

What changes on an exFAT drive

When you move a folder to an exFAT drive:

• Access lists are left out. Before every copy, Storage Studio checks whether the drive can hold access lists. exFAT can't, so they're skipped on purpose — otherwise the whole move would fail.
• File flags may be left out. Finder's Locked flag and the hidden flag are copied where the drive can hold them; on a drive that can't, the move still finishes without them.
• Shortcuts and permissions — Storage Studio's drive check warns that exFAT has known issues with both on macOS.

Everything else in What a move keeps is attempted as usual, and every copy is still checked before your original is removed. But a folder that has spent time on exFAT may come back without some of these details.

Everyday documents and media rarely carry an access list or a lock, so for them the difference is usually small. For folders where those details matter, or for a drive you'll keep apps and relocated folders on, use APFS.

%% caption: Moving a folder to an exFAT drive
flowchart TD
  A[Move a folder to an exFAT drive] --> B[Contents, names and dates are copied]
  B --> C[Access lists skipped - exFAT cannot hold them]
  C --> D[The copy is checked]
  D --> E{Can the drive hold the Locked and hidden flags?}
  E -->|Yes| F[Flags copied]
  E -->|No| G[Flags left out, move still finishes]
  F --> H[Original removed]
  G --> H

Should you reformat?

If the drive is only for your Mac, reformatting it as APFS gives you the best results. Keep exFAT only if you also need to plug the drive into a Windows PC.

Reformatting erases the drive, so do it carefully:

1. If Storage Studio already uses the drive, bring your folders back to your Mac first (Moving a folder back) and move any apps back from the Apps window — or move everything to another drive with Transfer to a New Drive.
2. Copy anything else on the drive somewhere safe.
3. In macOS's Disk Utility, select the drive and use Erase, choosing APFS.
4. Set the drive up again in Storage Studio — see Setting up your drive.

See also: Drive formats, exFAT, Access list, File ownership on external drives.