Copie e cole em sua guia de url:
data:text/html;charset=utf-8,<body OnLoad="document.getElementsByTagName('body')[0].appendChild(document.createElement('h1').appendChild(document.createTextNode('Heroku is awesome'))); document.body.focus();" contenteditable style="font-size:21px;font-family:'Corbel', Geneva, 'Helvetica Neue', Helvetica, Arial, sans-serif;max-width:800px;margin:0 auto;padding:2em;background-color:#1B1B24;color:white;">
Inspirado em https://coderwall.com/p/lhsrcq