You need an add-on for that: https://addons.mozilla.org/en-US/firefox/addon/add-on-compat...

That's not enough though. In about:addons all my add-ons are listed as compatible, but about:support still says that multiprocess is "disabled by add-ons". So YMMV.

EDIT: The gotcha is that the current release uses a whitelist of only about 20 extensions. If you have anything else, you need to force-enable the feature, even if your extensions are supposed to be compatible. https://hg.mozilla.org/releases/mozilla-release/file/FIREFOX...

How great would it be if that add-on were incompatible with multiprocess?

Firefox: Trouble managing your addons? Here, have this other addon!

But don't worry, we've bundled all these other tools that nobody wants into FF itself!

Yeah, as it turns out, when I installed it actually reported misleading info. (But then the official site misreported too.).

Uninstalled some of the tab extensions I had running and went for "Tab Center" from Test Pilot instead. I'm now running on multi-process and it seems quite a bit snappier overall. :)

How would you force-enable that feature?

Ah ok thanks, didn't realize that this info was only available because I have the add-on installed.