Organising files

The Merge option Finder hides

Updated 2026-07-31 · 4 min read

Dragging a folder onto a same-named folder on a Mac REPLACES it. This destroys data for every Windows switcher exactly once.

The danger

On Windows, dropping folder onto folder merges contents. On macOS, the default is Replace — the destination folder's contents are deleted and the dragged folder takes its place. The dialog says so; decades of Windows habit clicks through it.

The hidden Merge

Hold Option while dragging a folder onto a same-named destination, and the dialog gains a Merge button. Merge keeps both sets of contents, and for name collisions keeps both files (appending a number to the incoming one).

Merge appears only when Option is held *and* both folders contain items the other lacks — its absence otherwise is why people believe it does not exist.

The safer tools

ditto merges without dialogs, preserving metadata:

ditto ~/Source/Project ~/Destination/Project

Contents of Source are merged into Destination; collisions are overwritten by the source copy — so run it in the direction where the source is authoritative.

rsync merges with full control and a rehearsal:

rsync -avn source/ destination/     # dry run: shows what would copy
rsync -av  source/ destination/     # do it

Add --ignore-existing to never overwrite, or -u to overwrite only older files.

After merging

Verify by count before deleting the source:

find source -type f | wc -l
find destination -type f | wc -l

Then hunt duplicates the merge created — same name with an appended number — which a name-index search surfaces instantly.

Common questions

How do I merge folders instead of replacing on a Mac?

Hold Option while dragging onto the same-named folder; a Merge button appears in the dialog.

What is the difference between ditto and cp?

ditto merges into existing directory trees and preserves Mac metadata; cp -R replaces and can drop extended attributes on older systems.