This study aims to determine students' perceptions of the use of Alternative
Universe (AU) on the X platform in supporting English vocabulary building. This
study uses a qualitative approach with a case study design involving eight fifth
semester students at a private university in Bogor who actively read English
language AU. Data were collected through a Likert scale questionnaire and semi
structured interviews, then analyzed using Miles and Huberman's interactive
analysis model. The results showed that students had a positive perception of the
use of AU as an informal learning medium outside the classroom. Interesting stories
in AU increased learning motivation and encouraged curiosity about new
vocabulary. The presentation of vocabulary in the context of conversation and the
repetition of words in various episodes helped students understand and remember
vocabulary more easily. Thus, AU on the X platform can be an innovative and
enjoyable alternative medium in supporting incidental English vocabulary building.

Keywords: Alternative Universe (AU), X, student perceptions, vocabulary
building, English language learning.