This study involved four EFL high school students from a high school in Surakarta, Indonesia. It investigated 1) students’ perceptions of vocabulary learning through extramural Informal Digital Language Learning (IDLE) activities, and 2) the internal and external factors shaping those perceptions. Data collecting techniques included a combination of open-ended questionnaires, semi- structured interviews, and artifacts. The data analysis process involved familiarizing by carefully examining the data, coding and categorizing the data extracts, and recognizing thematic headings. The findings revealed that students had 1) positive perceptions, as they benefited from: a) their autonomy in exploring their interests, b) conducive environments characterized by minimal distractions and adequate facilities, c) abundant exposure to authentic language use, and d) the independence to take control of their personal language learning without external constraints, and 2) negative perceptions, which arose from: a) the absence of clear learning direction leading to inconsistent learning experiences, and b) limited explanations provided by tutors resulting in confusion. Those perceptions were shaped by 1) internal factors, including: a) individual interest, b) motivation, and c) learning frequency, as well as 2) external factors, including: a) the absence of teacher assistance, b) lack of competition among students, c) flexible learning time and location, and d) the availability of digital resources. Therefore, it is recommended that EFL students actively engage in extramural IDLE activities to enhance their vocabulary proficiency, with teachers still providing the necessary guidance and support to facilitate the process.
