The KeyboardEvent.metaKey read-only property returning a boolean value that indicates if the Meta key was pressed (true) or not (false) when the event occurred. Some operating systems may intercept the key so it is never detected.
Note: On Macintosh keyboards, this is the ⌘ Command key.
Warning: At least as of Firefox 48, the ⊞ Windows key is no longer considered the "Meta" key. KeyboardEvent.metaKey is false when the ⊞ Windows key is pressed.