If you don't touch the autoplay permissions for a site, Firefox seems to be attempting to use some heuristics to decide whether autoplay, such as calling ".play()" on an Audio object in javascript, should be allowed. What are these heuristics, and where are they authoritatively documented? [[https://developer.mozilla.org/en-US/docs/Web/Media/Autoplay_guide#autoplay_availability|MDN]] has some information but nothing Firefox-specific.