The Effectiveness of Duolingo to Improve Students’ Vocabulary Mastery in an Indonesian Secondary School

Vocabulary mastery is essential for English learning, yet students with limited prior exposure to English may experience difficulty developing basic vocabulary through conventional classroom activities. This study examined whether using Duolingo could improve vocabulary mastery among seventh-grade students at SMP Satu Atap Negeri 16 Sigi, Indonesia. A quantitative pre-experimental one-group pretest-posttest design was employed with all 24 seventh-grade students in one class. Data were collected using a 25-item vocabulary test administered before and after four treatment meetings of approximately 30 minutes each. The treatment focused on greeting expressions and vocabulary related to food and drinks through interactive activities. Descriptive statistics and a paired-samples t-test were used to analyze the data. The mean vocabulary score increased from 48.33 before the treatment to 91.67 after the treatment. The paired-samples analysis showed a statistically significant difference between the two measurements, t(23) = −10.919, p < .001. These findings indicate that Duolingo can function as a supplementary digital learning medium for vocabulary practice. Its use may provide repeated and interactive learning opportunities when integrated with teacher-guided classroom instruction.