In this paper, the development of a web application for self-access English vocabulary courses at a national university in Japan will be reported upon. Whilst the basic concepts are inherited from an old Flash-based online vocabulary learning system that had been long used at the university, the new HTML5-based app comes with several new features that are expected to assist students with effective vocabulary learning. Not only is it now made compatible with smartphones, it also enables students to visually check their own progress and their ranking in the class. According to the questionnaire survey conducted among its pilot users, almost 30% of them used the app on their smartphones. Overall, the users found the app beneficial--they especially liked features such as listening to word pronunciation, and checking their own ranking within the class. However, there is room for improvement regarding the usability of the app. [For the complete volume, see ED578177.]