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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. In Chrome, Google has a heuristic that tries to distinguish between those sites where autoplaying is generally welcome (Netflix and YouTube, for example) and those where it isn’t (those annoying sites that have autoplaying video tucked away in a corner to startle you when it starts making unexpected sounds). Firefox isn’t doing anything like that; by default, any site that tries to play video with audio will have that video playback blocked.
Firefox users will be able to grant autoplay audio permission on a site-by-site basis.
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 muted video to play back automatically.