This study examined the effects of self-explanation prompts on problem-solving performance. In total, 47 students were recruited and trained to debug web-program code in an online learning environment. Students in an open self-explanation group were asked to explain the problem cases to themselves, whereas a complete other-explanation group was provided with partial explanations and asked to complete them by choosing correct key-words. The results indicate that students in the open self-explanation condition (a) outperformed in a debugging task, (b) perceived higher confidence for their explanations, and (c) showed a strong positive relationship between the quality of their explanation and their performance. These results demonstrate the benefits of the open self-explanation prompts. Cognitive load of self-explanation and quality of explanation are discussed. (Contains 5 tables and 3 figures.)