External drives · Choosing a drive
Once I move files to the external drive, is that the only copy?
Short answer: Yes. A move frees space because the original leaves your Mac, so the external drive then holds the only copy. Back it up — Backup Drive copies it to a second drive, and Data Backup keeps versioned copies.
Yes — moving frees space precisely because the files leave your Mac. After a move is copied and verified, the original is removed and a shortcut takes its place, so the drive holds the only copy.
That makes backing up the drive important:
- Backup Drive (More → Drive) makes a full, verified copy of your working drive onto a second drive.
- Data Backup keeps versioned backups of the folders you choose.
- Time Machine can include an external drive if you remove it from Time Machine's exclusions.
Moving is not a backup; treat the fast drive like any important disk. See Backups.