Mozilla added that it is continuing to roll out multi-process Firefox for desktop users.
“Instead of running all of Firefox in one process, Firefox now runs in two processes: one for the browser’s user interface and another for web page content.”
“Today, more than half of desktop users are running Firefox in multiple processes.”
I'm on the beta channel, and I think I've had multiple processes for a while now. Can't say I've ever noticed a difference in performance between Chrome and Firefox on my PC though, other than Chrome taking longer to start up.