Your autoplay settings list will show any website permissions you have set that do not follow your default settings. Click that icon to open the Site Information drop-down panel, where you can change the Autoplay setting for that website. This option will always appear in the Control Center. Click the in the address bar to open the Control Center, where you can change the Autoplay sound setting. When Firefox is actively blocking media with sound on a website, you'll see a special icon in the address bar. The setting you select will apply to all media for all websites, except for specific autoplay site settings. After you have made your selection, click Save Changes.

The Allow Audio and Video setting will allow all media to autoplay.The Block Audio and Video setting will prevent autoplay for all media, including video, even though audio is muted.The default Block Audio setting will prevent autoplay for all media with sound.Use the Default for all websites drop-down menu to select how you want Firefox to handle media autoplay for all websites.Click the Settings… button next to Autoplay.(or enter autoplay in the Find in Options Preferences Settings search box). Select the Privacy & Security panel and go down to the Permissions section.Click the menu button and select Settings. In the Menu bar at the top of the screen, click Firefox and select Preferences.To always allow or block autoplay for all media with audio or video:

Stop chrome autoplay video