This study examined the type of code-switching by Poplack (1980) and its function by Mattsson and Burenhult (1999) in Literasi Bahasa Inggris UTBK 2025. This qualitative study explored classroom discourse and code-switching in a video of Miss Marlin teaching using descriptive research methods to analyze her utterances. Data were collected through YouTube video downloads, non-participant observation, and note-taking, with analysis guided by Miles and Huberman’s framework, focusing on data compression, visualization, and synthesis of findings related to code-switching categories. The study identified 103 code-switching data by Miss Marlin in "Literasi Bahasa Inggris UTBK 2025," with 83 intrasentential, 17 intersentential, and 3 tag-switching, primarily used to enhance student understanding. She employed all three functions of code-switching, such as topic switch (46), affective (45), and repetitive (12) demonstrating its effectiveness in clarifying complex concepts and building connections in the learning environment. In online learning, code-switching becomes even more crucial to overcome communication barriers, although reducing its use as students' English proficiency improves is essential for fostering independent language skills.