It's on by default. I used to be able to recommend Firefox on the grounds that it was different by design — non-commercial, open source, and supporting the open web. I can't do that now without being an obvious liar, hypocrite and/or idiot.
More importantly, on the mobile version at least it is very difficult to turn off all the way and randomly comes back. On the desktop I found the option buried down in the settings to turn it off easier, but I think I still have a bunch of random broken pocket icons scattered about now that I had to dig through about:config to actually remove.
