Move files between folders without duplicating them

If the move is on the same Volume:

• MacOS will "move" (by default) by adjusting their Directory entries, and no data blocks are copied.

• If you hold down the Option key, the reverse will be true (the files will be replicated at the new location). This will generally be shown as the pointer changing to a Plus-in-a-green-circle, indicating replicating.

if using APFS, the data blocks will also not be replicated, as APFS will simply create an additional reference and not use any more storage.

Volume-to-Volume:

• the default is to replicate on the new Volume, because that is the safest thing to do. Data blocks will be copied.

• Although there is a different shortcut to "Move", Best Practice is to manually delete the old copy.

Finder’s move/copy decision is primarily determined by whether the source and destination resolve to the same filesystem/volume, not simply whether they look like folders on the same Mac. On APFS, a same-volume move normally requires only metadata changes to the directory entries, so there is no file-data copy.... across volumes, Finder has to perform an actual copy because a directory entry cannot simply be moved between separate filesystems.

Also, the common claim that APFS “creates another reference” for a normal move is misleading.... APFS supports cloning and copy-on-write, but a normal same-volume move is fundamentally a namespace/metadata operation, not a second reference to the file’s data.

If Finder is unexpectedly showing Copy or producing a duplicate when both folders are visibly on the same volume, I’d check whether one path is actually a different volume, mounted APFS volume, network share, File Provider/cloud-backed location, or a filesystem boundary hidden behind a folder alias/symlink, df -h and mount in Terminal will tell you what filesystem each path actually resolves to.

The Option/Command modifiers also change Finder’s operation, so watch the cursor/action label rather than assuming drag-and-drop always means move.

Keeping in mind the above comments, if possible, it is often convenient to move files via command-C on the selected file and then option-command-v in the desired destination for the file.

If your file is in a Locked folder it will always be copied.

If this is the case use Get Info on the locked folder and deselect Locked.