Methods, systems, and apparatus, including computer programs encoded on computer storage media, for a responsive user interface. One of the methods includes receiving a page for a user device, the page including a panels. The method includes receiving a layout for the page, the layout defining a visual relationship between the panels. The method includes generating, by a computer system, a slide including a subset of panels to display on the user device, the subset of panels selected based on characteristics of the user device and the layout. The method includes sending the slide to the user device.