What a move keeps

When you Move, Merge or Relocate a folder between your Mac's built-in disk and an external drive, Storage Studio keeps far more than the files' contents. Here is exactly what comes across, what depends on the drive, and what doesn't.

What a move keeps

Terms in this table: extended attributes, Finder tags, Locked flag, hard link, sparse file, shortcut, access list, file ownership.

Why some things depend on the drive

Access lists. Storage Studio checks the destination drive before each copy. If the drive can hold access lists, they're copied. If it can't — exFAT is the usual case — they're left out on purpose, because insisting on them would make the whole move fail. Everyday files rarely carry an access list, so this seldom matters.

Locked and hidden flags. These are copied onto the checked copy just before the original is removed, and the original is unlocked so it can be removed. On a drive that can't hold a flag, that one flag is skipped and the move still finishes.

exFAT drives can't hold several things a Mac relies on. If you plan to keep folders on a drive long term, see What to know about exFAT drives.

Why ownership isn't kept

On your Mac, every file belongs to a user account. External drives usually have ignore ownership switched on by macOS, so the drive shows every file as belonging to whoever is using the Mac, and ownership written there isn't remembered. Storage Studio also runs as you, not as an administrator, so it can't hand a file to another account.

In practice this is invisible: the folders you move are your own files, and they come back as yours. If you share a Mac and move a folder that belongs to someone else, it comes back belonging to you. More in File ownership on external drives.

%% caption: How the drive affects what a move can keep
flowchart TD
  A[Start a move to the drive] --> B[Contents, names, dates, permissions, tags, links and sparse files are copied]
  B --> C{Can the drive hold access lists?}
  C -->|Yes| D[Access lists are copied too]
  C -->|No| E[Access lists are skipped so the move can finish]
  D --> F[The copy is checked]
  E --> F
  F --> G[Locked and hidden flags are copied where the drive can hold them]
  G --> H[The original is removed or replaced by shortcuts]

Moves that keep less

The list above is for folder moves between your Mac and a drive — Move, Merge and Relocate in Data Parking, and moves from Storage Inspector. Other ways of moving things keep less:

• Cloud accounts keep what each provider supports. Most keep the modified date; few keep anything Mac-specific. See Parking a folder in a cloud account.
• Send here and Data Transfers use the transfer engine. Between your Mac and a drive it keeps dates and permissions, but not everything listed above.
• Offloading an app packs it into an archive on your drive; see Offloading and restoring an app.

See also: How copies are checked, Drive formats, Moving folders safely.