Abstract: Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for generating a user interface that includes a viewport space of a digital content item; generating, based on user input, breakpoints of the viewport space based on a height, a width, or an aspect ratio of the viewport space; based on the breakpoints, generating formatting rules that each create a different version of the digital content item when the formatting rule is applied; and distributing, to a client device, the digital content item for display within an electronic document, including providing i) text or image content of the digital content item and ii) the formatting rules, wherein the formatting rules cause a client-side application to dynamically render and display an appropriate version of the digital content item based on the formatting rules and a size of a display area in which the digital content item is presented.

Abstract: Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for generating a user interface that includes a viewport space of a digital content item; generating, based on user input, breakpoints of the viewport space based on a height, a width, or an aspect ratio of the viewport space; based on the breakpoints, generating formatting rules that each create a different version of the digital content item when the formatting rule is applied; and distributing, to a client device, the digital content item for display within an electronic document, including providing i) text or image content of the digital content item and ii) the formatting rules, wherein the formatting rules cause a client-side application to dynamically render and display an appropriate version of the digital content item based on the formatting rules and a size of a display area in which the digital content item is presented.