News for hackers. Stuff that matters.
Re:Dear Google, Apple, Mozilla, and MS: Please End Auto-Play... by nextos on Sunday November 13, 2016 @06:46PM (#12946486)
Regarding 1 media.autoplay.enabled=false does the trick in Firefox about:config.
Re:Dear Google, Apple, Mozilla, and MS: Please End Auto-Play... by ergot on Tuesday November 15, 2016 @04:34PM (#12962431)
Or just disable mp4, webm, flash altogether in about:config. I typically view media in specially sanctioned browsers, just for viewing rich media.

E.G Chrome on windows 10 hooked up to a 4K Acer monitor via HDMI

You can harden FF also and remove a few other annoyances like the default PDF reader, etc:

https://github.com/pyllyukko/user.js/