This looks very interesting and has a Arch package in the AUR.I am typing this from a firejail firefox.
https://l3net.wordpr...jects/firejail/
https://l3net.wordpr...ozilla-firefox/
https://l3net.wordpr...bilities-guide/
There are quite a few pages of stuff to read and some of the comments are worth a read aswell.Of interest is the fact that you can run VLC-without internet access (or similar program) and also isolate programs like the TorBrowser and Dropbox.
I ran a quick comparison opening up FF with a page with video running and it does not seem to use up any more cpu or ram than a normal FF.