I believe this is the relevant comment:<p>&quot;<i>Apologies to all impacted by this transient configuration.  Firefox 43 users who do not have h.264 will get 360p VP8 until the configuration is updated early next year.  The very large majority of Firefox users watching YouTube have h.264. For them, and for user who get VP9, &lt;video&gt; MSE performs better overall than Flash.</i>&quot;