The presentation explores how advertising works on the different screens and why (which qualities of mobile video advertising are most important in breaking through to audiences and how the differential impact of creative length and screen size variables drive advertising effectiveness). The study analyses multiscreen use and behaviour among more than 13,500 consumers, interviewed by smartphone or tablet across 42 countries, and includes learning from parallel copy testing conducted across TV, online video and mobile video ads. The overall conclusion is marketers cannot simply assume that the device used is a good surrogate for media context, and that different ad formats definitely demand different creative approaches.