This is very annoying, since I like to keep many tabs organized in their container, but so often they are dissociated from their container, and then I have to open them again in the proper container, and then close the tabs outside the container. Likewise with any other tab of that container that I also did not happen to visit during session 2. Session 3 opens with that tab dissociated from its container. I forgot to hid that container before closing session 2. In session 2, I showed this container again, but did not go to that particular tab from session 1, so that it did not 'load'. Imagine, on session 1, I browsed to a page in a container that is not the first one in the list, and I hid this container before I closed session 1. the tab in that container has not been loaded during the previous session the container was not hidden before the previous Firefox session was closed, 2. That can be uncovered here: Mac: '3-bar' food selection button (or Firefox menu) > Preferences Linux: '3-bar' food selection button (or Edit menu) > Preferrals Windows: '3-bar' food selection switch (or Tools menu) > Options Any system: type or paste about. Other containers are dissociated from tabs, always and only if: 1. You deserve to collection Firefox to reclaim your session instantly at startup. The first container, that I use as my 'standard' container, and always is active in each session, is never dissociated from any tab. In the Font Book app on your Mac, choose File > Restore Standard Fonts. Happens to me every time, on every instance of Firefox I have on every computer (Ubuntu/Windows). Google Chrome, Mozilla Firefox, Opera and Microsoft Edge have removed support. NoScript (Restrictions disabled globally) Mozilla Firefox 80.0.1 (64-bit) - Portable version from Though, of course, sometimes URL can contain sensitive information (i.e. Just the URLs that were previously in containers got opened in non-container tabs, but cookies, logins, etc. In other words 'reopen in container' was never used. None of these tabs were ever reopened from a different container, all tabs were opened by either opening a container tab and then typing a URL or secondarily by opening a link from a container tab that opens a new tab (in the same container). Except one or two remain in their proper containers.

My old tabs, all of which were in containers, load in regular non-container tabs. My old tabs load in the same containers there in when I last closed the browser. I load up Firefox with 'Restore previous session' option clicked for startup. I just wanted to see if anyone else has had this error or if there are any thoughts on what might produce it (this would help me in testing scenarios to reproduce the error). This has only happened twice, so I am still trying to figure out how to reproduce the error.

Firefox restore session on startup