Default node icon. For any node if its icon property is not defined, then default icon will be used. The icon property is a css class for the icon span. See .nodes to see how to use icon for nodes. <span class="{icon}">...</span> The difference between img and icon is that img uses a div and a background image. The icon property uses a span and icon fonts, such as font-awesome. You can define it during object creation: $('#sidebar').w2sidebar({ name : 'sidebar', icon : 'fa fa-start', nodes: [ { id: 'id-1', text: 'Level 1' }, { id: 'id-2', text: 'Level 2' }, { id: 'id-3', text: 'Level 3' } ] }); Or any time after the object has been created: w2ui['sidebar'].icon = 'fa fa-star';