Energy is a critical resource for current mobile devices. In a smartphone, display is one of the most energy consuming components. Modern smartphones often use OLED screens, which consume much more energy when displaying light colors than displaying dark colors. In our previous study, we proposed a technique to reduce display energy of mo- bile web apps by changing the color scheme automatically. With this approach, we achieved a 40% reduction in display power consumption and 97% user acceptance of the new color scheme. In this tool paper, we describe Nyx, which implements our approach. Nyx is implemented as a self- contained executable file with which users can optimize en- ergy consumption of their web apps with a simple command.

A smartphone’s display is one of its most energy consuming components. Modern smartphones use OLED displays that consume more energy when displaying light colors as op- posed to dark colors. This is problematic as many popular mobile web applications use large light colored backgrounds. To address this problem we developed an approach for auto- matically rewriting web applications so that they generate more energy efficient web pages. Our approach is based on program analysis of the structure of the web application im- plementation. In the evaluation of our approach we show that it can achieve a 40% reduction in display power con- sumption. A user study indicates that the transformed web pages are acceptable to users with over 60% choosing to use the transformed pages for normal usage.