This study explores the self-efficacy and vocabulary mastery of students with digital gaming experiences as their affective and cognitive domain, along with the challenges in playing digital games as Informal Digital Learning of English (IDLE). The current alterations in educational sector due to the latest age development and the COVID-19 pandemic force the academics to use more the informal learning outside the classroom. They need an approach that can facilitate the students, especially the learners of English of Foreign Language (EFL), to practice the language daily. Playing games as a form of IDLE can accommodate the needs. The study applies a sequential qualitatively driven mixed-method which inspects 10 high school students with digital gaming experience out of 244. The study utilized a questionnaire, interview sessions, and receptive-productive vocabulary tests for the data collection. It is discovered that the students with digital gaming experiences has self-efficacy and good vocabulary mastery. There are also found some challenges regarding the implementation of IDLE in academic context and they need to be solved by involving many parties and stakeholders to achieve a holistic solution. Those findings imply that the study promote the application of IDLE, especially the digital gaming, within an academic context to sustain in-class teaching through out-of-class learning.

Keywords: Digital Games, English as Foreign Language, Informal Digital Learning of English, Productive Vocabulary, Receptive Vocabulary, Self-Efficacy