480px or greater: There is a known issue where some browsers will prevent small-format video from loading automatically. We believe this is an attempt to prevent obtrusive forms of advertising, but unfortunately the behavior is undocumented and varies by browser vendor, browser version, operating system, and even what other content is on the page.

A reliable solution for now is to make sure that the player is rendered at 480px or greater in width, at which point none of the browsers seem to interject. We're currently looking into solutions that don't rely on minimum dimensions, but for now this specific behavior is best avoided by the host page.