How to Merge Folders on Mac Without Replacing Files

Drag a folder into a place that already has a folder with the same name and Finder asks a dangerous question: Replace? Click it and the destination folder — including every file that existed only there — is gone, swapped for the one you dragged. What you usually want is a merge: one folder containing the contents of both. Finder can do it, but the option is hidden behind the Option key. Here's how it works on Ventura, Sonoma, and Sequoia, and what to use when Finder refuses.

The hidden Merge option

1. Start dragging the source folder toward its destination.
2. Before you drop, hold down the Option key (this also makes the drag a copy — you'll see a green +).
3. Drop. In the dialog, click Merge.

Finder combines the two: everything unique to each folder ends up in one folder with the shared name. Subfolders with matching names are merged recursively the same way.

What the dialog buttons actually do

• Merge — combines contents. Appears only under the conditions below.
• Keep Both — no combining; the dragged folder is kept alongside the original with a name like Reports copy. Appears when you drag without Option.
• Stop — cancels the whole operation. Always safe.
• Replace — deletes the destination folder and puts the dragged one in its place. Files that existed only in the destination go with it. Treat this button as destructive, because it is.

When Finder offers Merge — and when it won't

Merge has strict conditions, which is why it seems to appear randomly:

• You must be copying, not moving — that's why holding Option (which forces a copy) reliably summons it.
• One folder must contain items the other doesn't. Identical folders have nothing to merge.
• If both folders contain different versions of identically named files, Finder won't merge at all — you'll only see Stop and Replace. Finder refuses to decide which version wins.

That last rule is the common frustration: two Reports folders that share even one edited filename lose the Merge button entirely.

The reliable fallback: ditto in Terminal

Apple ships a command built for exactly this. ditto copies the contents of one folder into another, creating what's missing and preserving permissions and metadata:

# merge the contents of Source into Destination
ditto ~/Desktop/Reports-old ~/Documents/Reports

Everything from the source is copied in; files that exist only in the destination are untouched. The one behavior to understand: when both folders have a file with the same name, the source's version overwrites the destination's, silently. There is no undo, so if the destination might hold newer versions, copy it somewhere safe first (ditto ~/Documents/Reports ~/Desktop/Reports-backup) — then you can restore anything the merge clobbered.

Choosing winners with rsync

When both folders hold edited versions of the same files and you want the newer one to win regardless of which folder it's in, rsync gives you that control:

# copy from source into destination, but only files that are newer
rsync -av --update ~/Desktop/Reports-old/ ~/Documents/Reports/

The --update flag skips any file whose copy in the destination is already newer, so nothing recent gets stomped by something stale. Two syntax details matter: the trailing slash on the source means “the contents of,” not the folder itself, and -av preserves timestamps while printing each file it copies — so you get a receipt of exactly what moved. Run it with --dry-run added first to preview the plan without copying anything.

Check the result

After any merge, select the combined folder and press Cmd+I — the item count and size in Get Info should roughly equal the two originals minus duplicates. If the numbers look wrong, your backup copy has everything.

Comparing before you merge

Not sure what's actually different between the two folders? Compare them first so you know what the merge will do — how to compare two folders on Mac walks through the quick ways.