Merging folders on a Mac is kind of a pain. When you do it, Finder tries to overwrite any file with the same name with the newer version. That means it’s easy to accidentally erase a whole folder. How-To Geek shows off a better way to merge folders using Terminal.
If you want to merge folders properly use the
ditto command in Terminal. For example:
ditto ~/Desktop/Test ~/Downloads/Test
This will merge the Downloads/Test folder with the Desktop/Test folder, overwriting the contents of the destination folder with files from the source folder, while still keeping anything that’s different. You can also do this by option-clicking a folder and dragging and dropping it, but it doesn’t work as well. If you’ve been annoyed by Finder’s inconsistent merge options,
ditto should do the trick.