Short-video systems deliver videos only a few seconds or at most a few minutes long, in a personalized way, to billions of users around the globe. In the last few years, they have become increasingly popular for delivering societally beneficial content, such as microlearning, news, citizen reporting, advertising, user-generated content, testimonials, sports feeds, and more. Unlike long-form multimedia which is well-studied, short-video systems are unique in terms of the associated user behaviors, video and audio content, recommender algorithms, and the delivery pipelines that transport videos from content providers via content distribution networks (CDNs) and eventually to user devices. This transformative project will help improve both the efficiency of, and our understanding of, the class of short-video systems. The project plan draws on a unique and innovative combination of systems and networking design philosophies, along with machine learning (ML) techniques, complemented by real human user studies; this combination is essential for short-video systems because of their user-facing nature. The expected project outcomes include new video delivery techniques that use less compute and network resources and reduce consumption of user devices’ energy; new analytical understandings of the behavior of short video systems; and browser plugins and open software. Educational content will include course modules, including ones for online courses, focused on short-video streaming sy