I'm using the Developer Edition of Firefox. Previously, it was based on Aurora but now the Developer Edition is based on Firefox Beta. So, I was automatically upgraded from version 54.0a to 54.0b. Unfortunately, I've lost the checkbox for "Enable multi-process" when that happened and I'm not really sure what to do now. I had previously disabled the checkbox, since I was experiencing various problems when running the multi-process version. Now, I want to re-enable it to see if the problems are fixed and to make sure I get multi-process when it gets enabled by default for all users. The problem is, I can't figure out how to undo the setting I made, since the checkbox for it is gone. I've tried resetting some values in about:config but Firefox still only uses one process. What settings exactly did the checkbox that was present in 54.0a influence? Update: There seem to be four settings that control this behavior: browser.tabs.remote.autostart browser.tabs.remote.autostart.1 browser.tabs.remote.autostart.2 browser.tabs.remote.desktopbehavior Resetting them all to default doesn't enable the feature, so I guess unlike with 54.0a, multi-process is disabled by default for version 54.0b and I have to explicitly enable it. Does anybody know the difference between these settings?