Mac storage basics · Finding big files, Downloads and the Trash
Where do AirDropped files go on a Mac?
Short answer: To the Downloads folder (photos and videos may open in Photos instead). Large AirDropped videos often make Downloads grow quickly.
Files AirDropped to your Mac go to the Downloads folder (photos and videos may instead open in Photos, depending on what you choose). Large AirDropped videos are a common reason Downloads grows quickly.
Move what you want to keep somewhere sensible and delete the rest. See cleaning up Downloads.