Background <p>Migraine is a major source of disability in Korea, yet many patients remain underdiagnosed or undertreated. Traditional epidemiological studies are limited by recall bias and incomplete patient-reported outcomes. App-based headache diaries offer real-time, repeated measures of symptoms and treatment, enabling large-scale assessment to better understand migraine burden and treatment response. This study aimed to evaluate the large-scale implementation of a nationally distributed smartphone “Headache Diary” mobile application and describe migraine burden, acute treatment response, and functional impairment in real-world practice in Korea.</p> Methods <p>We conducted a retrospective, non-interventional analysis using self-reported data from the nationwide “Headache Diary” mobile application, developed by the Korean Headache Society. We included users who submitted at least one headache report between December 2020 and January 2025. Migraine/probable migraine were identified using an algorithm based on medication use and ICHD-3 criteria, while the remaining participants were classified into a non-migraine group (including tension-type headache or unclassifiable headache disorders). Acute-treatment failure was defined as pain relief reported after 2 hours or no effect. We also analyzed clinical characteristics, acute treatment patterns, and functional impairment associated with headache attacks.</p> Results <p>Of 23,713 users, 17,913 (75.5%) had migraine or probable migraine. Migraine patients experienced more severe headache intensity (55.5% vs. 13.7%), higher rates of premonitory symptoms (67.7% vs. 29.5%), more frequent identification of triggers (89.9% vs. 61.2%), and greater use of acute medications (73.1% vs. 23.8%) compared to non-migraine users. Among 211,302 headache attacks analyzed, 155,894 attacks were migraine, and 96,742 attacks were available for acute treatment effect assessment. Of the 86,301 triptan-treated attacks, 40.3% resulted in acute treatment failure. Adolescents (10–19 years) showed the highest failure rate (62.1%). Notably, attacks with premonitory symptoms (odds ratio [OR] 0.91, 95% CI 0.89–0.94), aura (OR 0.79, 95% CI 0.75–0.83), or potential triggers (OR 0.93, 95% CI 0.91–0.96) had lower odds of treatment failure. Functional impairment was reported in 36.6% of attacks, most as decreased work or study efficiency (21.0%) and reduced household activity efficiency (17.2%).</p> Conclusions <p>Nationwide, app-based data revealed that migraine patients in Korea frequently experience severe attacks, premonitory symptoms, and triggers, with substantial rates of acute treatment failure and functional impairment. These findings highlight the need for earlier recognition and timely intervention and suggest that real-time digital platforms can provide valuable insights for patient-centered migraine management.</p> Clinical trial number <p>Not applicable.</p>