Flat foot is a common reason for parents to visit orthopedic clinics. As the Internet has become an easy-search platform, parents often seek online educational materials before seeking out a professional. The aim of this study was to investigate the quality, readability, and understandability of such online materials for parents. An Internet search was performed for "flat foot" and "pes planus" using the Google search engine. The readability was evaluated using 6 different grading systems: Flesch Reading Ease Score, Flesch-Kincaid Grade Level, Simple Measure of Gobbledygook, Fry Readability score, Gunning Fog Index tests, and Automated Readability Index. The Patient Education Materials Assessment Tool test was used to assess the understandability. For quality assessment, the Journal of American Medical Association benchmark criteria and Health on the Net code were applied. One hundred nine websites were included and evaluated for readability, understandability, and quality. The mean readability grade for all websites was 10.5 ± 2.0. The mean Gunning Fog Index tests and Flesch-Kincaid Grade Level scores for all websites were 12.4 ± 2.2 and 9.7 ± 2.1 sequentially. The mean Coleman-Liau index score was 10.0 ± 1.5, and the average Fry Readability score was 9.9 ± 2.0. The automated readability index for all websites was 10.3 ± 2.5. The average Flesch Reading Ease score for all educational materials was 59.3 ± 10.1. The average Patient Education Materials Assessment Tool score for all educational materials was 81% (range, 70-87%). The mean Journal of American Medical Association benchmark criterion for all websites was 1.0, with a range from 1.0 and 2.0. Eighteen (16.5%) websites had Health on the Net certificates. Readability, understandability, and quality of patient education materials about flat feet on the Internet vary and are often worse than professional recommendations.