''<p>Lei12 [[#question-1511605|said]]</p>'' <blockquote>Why is the sessionstore.jsonlz4 generated from a private firefox window ? </blockquote> Private window tabs should not be listed in sessionstore.jsonlz4. Could you describe the steps that led up to finding private windows in the file? <blockquote>It is not private anymore if the session is stored in place of the regular session, which by the way happens not to be generated when the regular firefox window is closed while a private firefox window is still open. The private firefox window should have no effect on the regular session storage and should never be stored, all this is very confusing. </blockquote> If I understand what you're saying, if you close a regular window, but a private window is still open, then you quit Firefox, the regular window is not in the sessionstore.jsonlz4 file. Have you tried using either of these to restore the closed regular window: * "3-bar" menu button > History > Recently Closed Windows * (menu bar or Alt+S) History > Recently Closed Windows (This assumes that Firefox is set to restore your previous session windows and tabs at startup, or you use History > Restore Previous Session first.)