Private Browsing mode tabs mean that no data is stored in the Firefox profile folder, but is kept in memory. Container tabs means tabs in different containers are isolated from each other. Container tabs do not work in Private Browsing mode.

See also:

• https://wiki.mozilla.org/Security/Contextual_Identity_Project/Containers
• https://support.mozilla.org/en-US/kb/containers

• Options/Preferences -> General -> Tabs: Enable Container Tabs

Hello and thanks for the reply. So I'm trying to understand.

you say: 'Container tabs means tabs in different containers are isolated from each other.'

So this means, that in Private Browsing mode, tabs are not isolated from each other? I'm worried about cross-tracking in private mode.

Please can you verify this? thanks again for your time :)

Yes. In PB mode tabs aren't isolated from each other and all tabs share the same (in memory) cookie jar and thus for instance existing third-party cookies are possibly send.

So then I see a major advantage of Containers over Private Browsing mode. I think that a table with the differences would help others, but thank you for your answer :)