It is assumed that web-based dynamic assessment will continue to thrive and have a profound role in pedagogy. In this regard, an explanatory sequential mixed-methods design was selected to consider the effect of web-based dynamic assessment on learners' autonomy. A sample of 60 high school EFL learners was selected non-random for this purpose, and they were categorized into two groups web-based dynamic assessment and the control group based on the convenience sampling method. the learners’ autonomy questionnaire was used as a data-gathering tool for the pretest and posttest in autonomy. The high school students were exposed to web-based DA via a designed web, based on the student's level and need in grammar. However, control learners learned grammar through the traditional or conventional method of instruction. Based on Mann-Whitney U-test results, the learners’ autonomy means scores in web-based DA increased in comparison to those of the control group. The platform and methods employed in this study produce results that are encouraging for the field of language instruction and could produce motivational outcomes in the future. The pedagogical implications of the study will be discussed. Manuscript profile