Abstrak
The goal of this research was to assess students’ vocabulary mastery using the Simpler application. This type of research was pre-experimental. Purposive sampling was applied in this study, and the study selected one class as the research sample from VII-3, consisting of 31 students at SMPN 7 Tarakan. The t-test was used to analyze the data. The data analysis revealed that the students’ score before treatment was 48.19, and after treatment, there was a significant increase of 78.00. It was concluded that the Simpler application was able to make significant progress toward students’ vocabulary mastery. This study has implications for the use of media in English learning, and the Simpler application has a positive impact on teaching vocabulary.