The ascent of social media platforms as video destination sites is having a dramatic impact on the viewing behaviour and screen choices of consumers. Our research shows that social-media video platforms are heavily segmented around age with Snapchat and Instagram showing huge skews to the very youngest age group, while both YouTube and Facebook trend to average for video usage by age. The age skew is mirrored in a significant device skew for video viewing, with the smartphone being the most important viewing device for Snapchat and Instagram video users. The PC or laptop remains a more important device for both Facebook and YouTube. The interaction of age, device and platform choice has wide-ranging implications for digital-native content production and social media strategy. Until relatively recently, the larger-screened PC and Smart TV where generally seen as more important viewing devices for video, and while this may still apply for longer-form content, youth-driven video sites and the growing importance of short-form and digital native video in the overall entertainment mix means that the smartphone will increasingly represent the key video screen for regular viewing when moving beyond the traditional TV set. More insight on digital-native and short-form content is contained in our new free-to-download report, published by MIP TV: Digital Native Strategy and Short-Form Content.