The default is to still auto-play silent movies (movies with no audio track or with the muted flag). If you're just using this for a background effect, the best

The default is to still auto-play silent movies (movies with no audio track or with the muted flag). If you're just using this for a background effect, the best solution is to just get used to the fact that for a minority of users, the video won't work and you'll have to fill in something else (don't use a 50MB GIF, just go with something non-animated!), but a majority of users will still get the silent video.