Objective <p>This study aims to explore the associations between napping and subjective sleep quality and daytime functioning in insomnia patients, providing a valuable reference for the standardized diagnosis and treatment of insomnia disorders.</p> Methods <p>We conducted a survey using the “Good Sleep 365” application and collected sleep diary entries from patients with insomnia. On the basis of self-reported sleep diary data, the participants were categorized into a nap group and a nonnap group. We then analyzed and compared the differences in nighttime sleep and daytime functioning between the two groups.</p> Results <p>We collected a total of 97,471 user sleep diary entries. Comparative analysis revealed significant differences in sleep quality, sleep latency, and daytime functioning between the two groups. The proportion of participants in the nonnap group who reported good sleep quality, fell asleep within 30&#xa0;min and exhibited optimal daytime functioning was significantly greater than that in the nap group (all P-values &lt; 0.001).</p> Conclusion <p>Based on a large-scale investigation of Chinese insomnia patients, this study demonstrates significant associations between napping behavior and compromised sleep outcomes, including prolonged sleep latency, reduced sleep quality, and impaired daytime functioning. While the cross-sectional design precludes causal inference, these robust findings underscore the clinical relevance of napping assessment in insomnia management and provide an empirical foundation for developing culturally adapted sleep hygiene recommendations for Chinese populations.</p> Clinical trial number <p>Not applicable.</p>