Mozilla writes that with the launch of Firefox 66 on March 19, audible autoplay audio or video will be blocked on a newly opened site. You’ll only hear the sound following a user interaction that initiates the audio, such as hitting the play button. Muted autoplay videos—those without sound or that are muted by default—will still play automatically.
For any sites where people might want to allow autoplaying videos, such as YouTube, users can click on the new icon in the Firefox bar and give permission to allow autoplay sound.
