Using Facebook Container many times a week for about 6 months now. On a crowded up-to-date Firefox Nightly with Conex, Tree Style Tabs and other add-ons. Honnestly works almost flawlessly :-)
PS One can check if FC lets cookies alive in FF's Settings or using a privacy extension.

Uraaa

To me more important thing about this is facebook, instagram doesn't show adds related to my search history. So, I am very much happy with this addon. Thank you Firefox

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Would be nice if it was possible to disable the black bar above the tabs.