When you copy a file on an Apple computer, it is placed on the clipboard. A Mac's clipboard is stores the last copied or cut item for quick recall. When your clipboard contains a large image, it consumes system memory and slows down browsing speeds. You can clear virtually all of the clipboard's data by copying a blank piece of textual data. When you copy a small or blank piece of text, this overwrites the existing clipboard files, speeding things up and getting rid of the last item you cut-and-pasted.
Open a blank note pad or word processing document on your Mac.
Press the "Space" key.
Click and drag your cursor over the space.
Press "Command" and "C" to copy the blank text to your clipboard. This clears the existing clipboard data, replacing it with a blank space.
You can click on the “Finder” button, click “Edit,” and select “Show Clipboard” to verify that the clipboard is empty. When you restart your Mac, the clipboard is automatically cleared.