• EIVIND MJELDE Dept. Information Science and Media Studies, University of Bergen P.O.Box 7802, N-5020 Bergen, Norway
  • ANDREAS L. OPDAHL Dept. Information Science and Media Studies, University of Bergen P.O.Box 7802, N-5020 Bergen, Norway
Keywords: Adaptive Images, Clown-Car Technique, content-delivery network, domain sharding, HTML 5.1 pictures, HTTP/2, image sprites, lazy loading, Picturefull, responsive images, responsive web design, symbol fonts, web-browser load time, web-resource compression, web-resource concatenation, web-resource minification


Modern device-agnostic web sites aim to oer web pages that adapt themselves seam- lessly to the front-end equipment they are displayed on, whether it is a desktop com- puter, a mobile device, or another type of equipment. At the same time, mobile devices and other front-end equipment with limited processing powers, screen resolutions, and network capacities have become common, making front-end performance optimisation in general, and load-time reduction in particular, a central concern. The importance of load-time reduction is exacerbated by the proliferation of multimedia content on the web. This paper therefore reviews, evaluates, and compares available load-time reduction tech- niques for device-agnostic web sites, grouped into techniques that improve client-server communication, optimise UI graphics, optimise textual resources, and adapt content images to context. We evaluate the techniques on a case web site using both desktop and mobile front-ends, in a variety of settings, and over both HTTP/1.1 and HTTP/2. We show that each technique has its pros and cons, and that many of them are likely to remain useful even as HTTP/2 becomes widespread. Most techniques were clearly benecial under at least one of the conditions we evaluated, but most of them were also detrimental in certain cases | sometimes drastically so. Hence, load-time reduction techniques for device-agnostic web sites must be selected with care, based on a solid understanding both of usage context and of the trade os between the techniques.


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