In summary: trying to create keyboard shortcut commands on the web and the option key on windows doesn't seem to have a 'keyup' event in Firefox. I've illustrated this in this pen: https://codepen.io/dmetivier/pen/BmGLwV?editors=1111 Notice how pressing the option key doesn't print twice with full press and depress of the option key. Pressing the option key in FF brings up the menu bar, is there any way to disable this via JavaScript? Or is it just an oddity quirk that I'll have to just deal with? Thanks in advance!