This worked perfectly for years. Nowadays, Firefox is good enough at blocking auto-playing media that I no longer need this add-on, but thanks for all the years of service 🙏

Works perfectly

Works great with latest Firefox Quantum even though it's been 3 yrs not updated.

Finally found something that works and this mutes also the first tab automatically.

Thanks! Good function. It must be build-in in Firefox.

It very easy to use it. There are no problems with it. I would like to use it. It useful. And I share it with my friends.