This quantitative research examines Grammarly's impact on 60 Jordanian EFL students' writing. 60 students are enough to derive statistically significant conclusions about Grammarly's effects on writing. An experimental group of 30 students uses Grammarly while writing, whereas a control group of 30 students does not. Both groups write the identical assignments and are assessed using specified criteria. A pre-test compares both groups' grammatical correctness, vocabulary, and writing quality. After the pre-test, the experimental group uses Grammarly, while the control group does not. Students' writing skills are retested following the intervention. Grammarly's impact on EFL Jordanian students' writing is quantified by analyzing pre- and post-test results. T-tests or ANOVA are used to compare experimental and control group mean scores. Grammar, vocabulary, and writing quality are compared between the two groups. This study adds to the quantitative research on EFL online grammar correction tools. Grammarly's effects on EFL Jordanian students' writing abilities would assist educators and practitioners to decide whether to use such technologies in language training.