Currently, all Indonesian regions are experiencing a severe pandemic condition that affected all fields, including the education sector. The education system that is usually face-to-face has to turn online, which forces students with teaching staff to carry out the learning process from home. With online-based learning, teachers and students can take advantage of online learning-based platforms, like Google Classroom, to implement Self-Directed Learning (SDL), where there are adjustments to learning devices and material to be taught online and achieve the competencies to be trained. By using the preexperimental design method, the type of research used was one group pretest-posttest design. This article aims to apply Self-Directed Learning (SDL) in online-based high school physics learning on the subject of Newton's Law. The data analysis technique used is implementation of the learning process, normality test, paired t-test, and n-gain analysis. The application of Self-Directed Learning (SDL) is declared effective if the value on the final test (posttest) has a high value compared to the value of the initial test (pretest), as well as an increase in the results of the application of Self-Directed Learning (SDL) which is shown from the n-test. gain in the high category. In conclusion, the results of the application of Self-Directed Learning (SDL) can be done practically and are categorized as very good. The application of SDL is able to improve students' cognitive abilities in online-based physics learning for Newton's Law material.