[fiveseven_]

I believe it is enabled by default now, and the value in about:config is `media.block-autoplay-until-in-foreground`

[cpeterso]

Thanks for the pref name. The feature is currently enabled by default only in the Firefox Nightly channel but you can use the pref to enable it in the Beta or Release channels.

https://bugzilla.mozilla.org/show_bug.cgi?id=1352014

[bigbugbag]

It's disabled by default on regular firefox.

I prefer to disable media.autoplay.enabled which is enabled by default.