Last year, Chrome introduced changes to try to prevent the persistent nuisance that is pages that automatically play noisy videos. Next month, Firefox will be following suit; Firefox 66, due on March 19, will prevent the automatic playback of any video that contains audio.
Mozilla’s plan for Firefox is a great deal simpler, and a great deal stricter, than Chrome’s system.
Firefox users will be able to override this block on a site-by-site basis, so those sites where autoplay is inoffensive can have it re-enabled. This permission is automatically extended to sites that have previously been granted access to microphones or webcams, so that audio and video communications apps built using WebRTC will work as expected. Firefox will also allow video to play back automatically.