Evaluating the reliability and quality of viral myocarditis educational content on TikTok and Bilibili

Viral myocarditis (VM) affects over 1 million people yearly worldwide and may trigger arrhythmia, heart failure, or sudden death, bringing heavy clinical and economic burdens. TikTok and Bilibili are vital health information hubs, yet unregulated VM video content lacks quality evaluation on Chinese platforms. This cross-sectional study assessed VM video reliability and completeness on both platforms to support evidence-based health guidance. Data collection finished on February 15, 2026. We collected the top 100 default-ranked videos per platform via incognito new accounts searching "viral myocarditis." After screening out ads, irrelevant, recent and duplicate videos, 180 clips (TikTok = 91, Bilibili = 89) were analyzed. Two trained cardiologists scored videos with the 0 to 5 modified DISCERN (instrument for evaluating health information quality) scale and 1 to 5 Global Quality Score and graded 6 disease domains' completeness using a 3-point scale. Nonparametric tests and Spearman correlation were adopted, with P < .05 as the statistical significance threshold. TikTok videos had significantly higher median likes, comments, saves, and shares (all P < .001), while Bilibili videos were longer (139 vs 95 seconds, P = .002). Professional creators accounted for 71.43% of TikTok uploads versus 44.94% on Bilibili, which hosted more nonprofessional contributors. TikTok fully covered symptoms best (40.66%) but ignored epidemiology (83.52% uncovered); Bilibili offered more complete etiology, prevention, and symptom explanations yet lacked epidemiological content. Bilibili contained far more high-rating DISCERN (4-5) and 5-star Global Quality Score videos and no 1-point low-quality clips, unlike TikTok. Engagement metrics were strongly positively correlated on both platforms; video duration weakly negatively correlated with interaction on TikTok but moderately positively correlated on Bilibili. Inter-rater reliability was excellent (r = 0.81-0.96). Bilibili's VM videos outperform TikTok in information completeness and overall quality. TikTok's higher traffic often favors low-quality content, and preventive knowledge coverage is insufficient on both platforms. Such gaps arise from distinct user groups, content formats, and algorithms. Optimized algorithms, medical creator certification, and differentiated science communication can standardize VM online education and help patients access reliable disease management knowledge.