How to reverse the F keys default functionality I am newbie Mac user and I recently stumbled upon this annoying F6 problem: when I debug in Xcode or Eclipse, I must use fn+F6 to run the debugger. By default, F6 is the function key to adjust the keyboard light. How can I reverse its functionality, in order to use F6 for the debugger and fn+F6 for the keyboard light?
System Preferences -> Keyboard -> Keyboard tab -> check "Use all F1, F2, etc. keys as standard function keys"

UPDATE: If you have a touch bar Mac you'll want System Preferences -> Keyboard -> Keyboard tab -> "Touch Bar shows" -> "F1, F2, etc. Keys"