Abstract
This study was conducted in response to the low level of junior high school students understanding of spatial geometry concept in mathematics learning. The limited use of interactive instructional media often causes students to experience difficulties in visualizing and interpreting three-dimensional objects in real-life situations. Therefore, inovative and engaging learning media are needed to improve students’ participation and conceptual understanding, particularly through the use of GeoGebra-based interactiv media. This research aimed to investigate the effec of GeoGebra-based interactiv media on students understanding of spatial geometry concept. The study employed aaquantitative method using a quasi-experimental approach with a pretest–posttestccontrol group design. The population consisted of allaeighth-grade student of SMPIT Jihadul Muslimin Batu Pengilik, East Lombok, in the 2025/2026 academic year. Samples were selecteduusing a cluster random sampling techniqe, with class VIII A assigned as theeexperimentaligroup and class VIII B assthe control group, each consisting of 20 students. The experimentallgroup received instruction throught GeoGebra-based interactive media, while the control group used PowerPoint media. The research instrument was a validated test of students understanding of spatial geometry concept. Data analysis was conducted using descriptive statistics, the Shapiro–Wilk normality test, Levene’s Test for homogeneity and the Independent Sample t-test with the assistance of SPSS 25. The findings revealed that the experimental group achieved an average posttest score of 83.70, while the control group obtained 75.90. Hypothesis testing produced a significanc value of 0.001 < 0.05, indicating that GeoGebra-based interactive media significantly affected students’ conceptual understanding. In addition, the pretest analysis showed no significan differenc between the two group (Sig. = 0.128 > 0.05), indicating relatively equivalent prior abilities. Effec size analysis using Cohen’s d showed aamoderate effec on the pretest (0.50) and a strong effect on the posttest (1.17). These results demonstrate that GeoGebra-based interactive media effectively improves students’ understanding of spatial geometry concepts through interactive and meaningful learning experiences.