Purpose: The paper reports a study that was intended to develop a self-assessment instrument to measure high school students' readiness for pursuing independent online learning. Design/methodology/approach: The instrument was developed through the following steps--(1) developing the draft, (2) checking the instrument's face validity, and (3) testing the instrument's validity, reliability and discriminant capacity using PLS analysis. Findings: The study has developed a tool to self-assess high school students' readiness for independent online learning. The instrument consists of 36 statement items and is statistically proven to have good reliability, construct and indicator validity and a discriminating power. Research limitations/implications: The instrument items were designed to fit the context of Indonesian high school students. However, only responses from high school students in rather urban areas were used to test the validity and reliability of the instrument. This could imply that the instrument is only accurate in urban settings. Practical implications: As a result of the research, a tool to assess high school students' readiness for independent online learning has been created. To better prepare students for independent online learning endeavors, the school might use the results to enhance areas that need improvement. Originality/value: The study succeeded in developing a contextualized self-assessment tool for measuring Indonesian students' independent online learning readiness.