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Most modern web browsers mute audio content that plays automatically on websites that users visit on the Internet.

Firefox started to block autoplaying audio automatically with the release of Firefox 66 which Mozilla started to test in mid-2018 already in development versions of the web browser.

Google Chrome, and most Chromium-based browsers, block audio from playing automatically as well on sites.

Mozilla plans to improve Firefox's autoplay-blocking capabilities with the release of Firefox 69. Firefox 69 is scheduled for a September 3, 2019 release.

Current versions of the Firefox web browser, that is any version pre-69, block audio from playing automatically when you visit Internet sites. Video content is not blocked in the web browser even if sites play videos automatically when you open them.

Starting with Firefox 69, Firefox users will get an option to add video to the autoplay-blocking behavior of the web browser.

The new Autoplay permission replaces the "block websites from automatically playing sound" option in the Firefox options.

A click on the Settings button associated with the permission opens a new configuration overlay in the browser.

There you find an option to set the default level of blocking for all sites and to manage websites with custom autoplay permissions.