Vocabulary is essential for clear communication, academic achievements, and future prospects. However, numerous students struggle to learn a wide array of words, grasp their context, and pronounce them accurately. The advent of digital technology has led to the creation of language learning apps like Duolingo, which serve as engaging, gamified resources that facilitate vocabulary acquisition. This research intends to methodically examine existing studies on the effectiveness of Duolingo in enhancing English vocabulary skills among junior high school learners through a structured literature review. Utilizing the PRISMA method, twenty-four pertinent experimental studies published between 2020 and 2025 were chosen from platforms such as Google Scholar and Semantic Scholar. These studies were assessed descriptively to uncover typical trends, techniques, and results pertaining to Duolingo's role in vocabulary education. The outcomes indicate that Duolingo significantly improves students’ vocabulary performance, motivation, and engagement, thanks to its game-like qualities and adaptable learning setting. Nonetheless, several studies point out drawbacks, including the lack of comparative studies with alternative educational tools and a limited focus on long-term retention. Overall, the findings affirm Duolingo’s effectiveness as a valuable supplementary resource for learning vocabulary, aiding teachers in creating innovative and interactive English language teaching methods. Future studies are encouraged to investigate its application in classroom environments and its effects on various types of learners