Notably, it'll remain disabled by default if you're using extensions (pretty much everybody here who is running Firefox?): <i>The groups that will have to wait a bit for E10S account for about half of our release users and include Windows XP users, users with screen readers, RTL users, and the largest group, extension users.</i><p>You can manually enable it, though[0]: <i>However, if you want to permanently opt-in, you can do so with a simple pref change. Just go to about:config and toggle browser.tabs.remote.autostart to true. On your next restart, e10s should be active. To verify that it is active, go to about:support and look for a number higher than 0 in "Multiprocess Windows".</i><p>I didn't realize they had this kind of fine-grained control over A/B-testing in their Firefox beta population, as Asa puts it: <i>We have all the knobs.</i> I understand where they are coming from, but it feels a bit weird to have a piece of software running on my computer checking in with a remote server to enable/disable functionality.<p>[0] <a href="https://wiki.mozilla.org/Electrolysis" rel="nofollow">https://wiki.mozilla.org/Electrolysis</a>