Qualitative study was used to analyze the data in this research. The participant of this research are two students of Junior High school in Central Java, Indonesia. The participants meet the requirements because they are smartphone users daily and are used to dealing with English-language content on a casual. They also study English as a Foreign Language at school, with the intermediate level determined by their report card and the most recent English test administered by the school. The main data of the study is based on diary or narrative of the participants’ experience, supported by an interview and artifacts. The data was analysed based on thematic coding of vocabulary and experience theoretical concept and indicators. The findings of the study reveal that participants have cultivated a new experience while utilizing Duolingo as a tool to enhance their vocabulary mastery. This new experience is indicative of the platform's efficacy in meeting the diverse needs of learners in terms of sensory engagement, individual experiences, and understanding of language concepts. Furthermore, for understanding vocabulary, which encompasses the dimensions of form, meaning, and use, Duolingo has effectively addressed and facilitated mastery in each of these aspects. The participants' exposure to a diverse range of quizzes within Duolingo serves as a concrete demonstration of the platform's commitment to enhancing vocabulary skills across these dimensions. The data analysis underscores the positive impact of Duolingo on the participants' vocabulary proficiency, substantiating its effectiveness in providing a comprehensive and well rounded approach to word knowledge. Duolingo's user-friendly interface and flexibility make it an effective, enjoyable tool for personalized language learning. As a dynamic platform, it fosters continuous improvement in English proficiency, offering valuable benefits for students beyond traditional classroom settings.