Contemporary young students in Asia and in the Nordic region are increasingly learning English outside the classroom by using technology (a.k.a. Informal Digital Learning of English [IDLE]). This comparative study examines to what extent "IDLE" influences Korean and Swedish students' "willingness to communicate in a second language (L2 WTC)," a critical antecedent affecting actual L2 communication behaviour. After having achieved a cross-cultural equivalence of the research instrument, Korean (n = 388) and Swedish (n = 144) secondary school students were surveyed. Results of hierarchical regression analyses show that "Frequency of IDLE" (the total amount of IDLE activities) predicts both cohorts' L2 WTC, while "Receptive IDLE activity" (consuming English content) and "Productive IDLE activity" (producing English content) are predictors for only Koreans' L2 WTC. Results suggest that Korean and Swedish students tend to more frequently initiate English communication when engaging in IDLE activities. Results also suggest how Receptive and Productive IDLE activities could uniquely facilitate the L2 communication behaviour of Korean EFL learners, who learn English in a linguistically and culturally homogeneous society. Apart from context-specific pedagogical implications, this study could provide insights for L2 learners worldwide who have been learning language remotely with minimal supervision.