My work has broadly focused on developing techniques that help developers to improve the quality of their web and mobile apps. In particular, my group's work has focused on areas that have become of increasing importance: energy consumption, appearance of the user interface (UI), and security. For energy consumption, our work has focused on techniques that enable developers to understand and change their mobile apps' energy consumption; leading to the development of techniques that provide developers with fine-grained insight into how energy is consumed by their apps and help them to make changes that can save significant amounts of energy. For the UI appearance, my group has focused on techniques that can more efficiently and more accurately find errors in an application's UI. As part of these efforts we have also developed many analysis techniques for mobile and web apps.