Mac OS X El Capitan, Option key alone as keyboard shortcut I am using Macbook Air Mid2012 with El Captian 10.11.3 version.

I have two languages installed (two input sources). Currently my shortcut to toggle the language input is "CMD + space." I would like to use the option key on the right-hand-side as a shortcut for input source toggle.

System Preferences - Keyboard - Shortcuts - Input sources won't allow me to specify option key alone as a valid shortcut.

Is there anyway to do this?

Thank you!
It seems that modifier keys like cmd, ctrl, option, shift cannot be used alone and have to be combined with other keys as shortcuts. Alternatively you may also try using option + space as the shortcut to toggle input sources.