The vast number of online educational videos available at the moment has generated an emerging area of research concerning their level of suitability. This study considers the epistemic quality of educational videos on mathematics, focusing on the specific content of directly proportional distributions. A qualitative study is used, based on the application of theoretical and methodological tools from the onto-semiotic approach to knowledge and mathematics instruction, principally the notion of epistemic suitability and the identification of algebraic levels. The sample consists of the 31 most popular videos in Spanish on YouTube ™ on directly proportional distributions. Analysis reveals interesting results on these kinds of resources. In general, it is observed that they are weak in epistemic suitability, which does not seem to affect their level of popularity. Moreover, the existence of videos with inaccurate arguments or incorrect procedures, together with the diversity of algebraic levels used, indicates that teachers should be careful when selecting them and only recommend those that better suit their students’ needs.