A method of presenting an optical code on a display is described. The method comprises: presenting the optical code in a first format at a first time period so that the optical code can be captured and decoded by a mobile device, such as a smart phone. The method also comprises presenting the optical code in a second format at a second time period. The second format is visually different to the first format to a human but when captured and decoded by a mobile device, the second format produces the same decoded results as the first format.