By Alvin Alexander. Last updated: June 4, 2015
To create an em dash on Mac OS X systems, type this keystroke:
[Shift][Option][-]
That’s the “Shift, Option, and the hyphen keys” pressed on your keyboard, simultaneously. That keystroke will give you a “—”. It seems to work properly in every Mac OS X application I’ve tested.
As for an “en dash,” don’t use those, they’re confusing (though you can figure out how to create one from this em dash tip).