It's wonderfully complicated, isn't it?

silvuss said

The problem is that: 1) I log into a website; 2) I clear the cookies using both the "Clear Data..." and "Manage Data" buttons (marking all the options); 3) Firefox says "Your stored cookies, site data and cache are currently using 0 bytes of disk space." 4) I refresh the page of the website; 4) the website still shows that I am logged in; what is more, the developer tools->Storage shows some cookies (I do not know whether it is all of the expected cookies for that website).

Maybe this varies among sites??

If I:

1. Log into Google from https://www.google.com/
2. Open the Options/Preferences page in a separate tab and use Clear Data with both boxes checked
3. Reload the Google page (Ctrl+r)

I'm logged out. (I do not use a password manager to log me in to the site.)

On some pages that allow caching, it's possible Firefox doesn't actually reload from the server when you click the reload button or press Ctrl+r. Instead, Firefox may check whether the page changed since the time it was cached. To bypass that, you can force a full reload by either Shift+clicking the reload button, or pressing Ctrl+Shift+r.

Note: The Storage Inspector list (Shift+F9) doesn't reload correctly using the arrow button above the list. I have to close the Developer Tools and re-open it after step 2 to confirm cookies were deleted. As a confounding factor in this particular case: On Google, every time I switch back to the tab with the Google home page, between two and four cookies are updated or recreated. However, the cookie with my session ID that would keep me logged in is not re-created.

What is more surprising to me: 5) After the above steps, when I set the option "Block cookies and site data->Type blocked" to "All cookies" and then refresh the page, the website says that I am NOT logged in, but the cookies ARE still shown in the developer tools->Storage; 6) after that, when I set this option to "All third-party cookies", after refreshing the website says that I AM logged in "again". The cookies are still shown in the developer tools->Storage.

When you change the cookie permission applicable to a site, Firefox does not clear previously set cookies automatically. So those cookies are still available to send to the site if the site regains permission to set them (for example, because you first blocked cookies, then made an exception for the site).

For #5, because the site no longer has permission to set cookies, Firefox no longer sends its previously set cookies with your requests. Accordingly, the site no longer recognizes you as having a live session, and shows the page a logged-out person would see.

For #6, Firefox resumed sending the site its previously set cookies since it is the "first party."

Thanks for such a quick reply!

jscher2000 said

Maybe this varies among sites?? If I:

1. Log into Google from https://www.google.com/
2. Open the Options/Preferences page in a separate tab and use Clear Data with both boxes checked
3. Reload the Google page (Ctrl+r)

I'm logged out. (I do not use a password manager to log me in to the site.)

Hm, it is possible. Sorry for that I have not checked it, it is so simple. Now I see that three other websites that I have now checked clear cookies, and this ends session (they display that I am not logged in).

Now I also see that Firefox reports cookies of the first site that I have checked, too, if I refresh the "Preferences" page... I did not think about such a thing, but it seems to be the case (I though that Firefox reads the database every time I click on the button "Clear Data..."). And Firefox seems to correctly clear cookies.

I wonder why cookies were not removed earlier; I thought that my steps were the same as now... Well, possibly I did something different.

On some pages that allow caching, it's possible Firefox doesn't actually reload from the server when you click the reload button or press Ctrl+r. Instead, Firefox may check whether the page changed since the time it was cached. To bypass that, you can force a full reload by either Shift+clicking the reload button, or pressing Ctrl+Shift+r.

Thank you for the keyboard shortcut, I did not know about it. I always use CTRL+F5 if I want to reload cache (although you are right – this time I have forgotten to use it, so I do not know whether that was the case or not).

Thank you again for such a explicit explanation. : - ) Now I see all the process more clear. I always look for such clarity and understandability on the internet.

silvuss said

Now I also see that Firefox reports cookies of the first site that I have checked, too, if I refresh the "Preferences" page... I did not think about such a thing, but it seems to be the case (I though that Firefox reads the database every time I click on the button "Clear Data..."). And Firefox seems to correctly clear cookies.

Yes, I forgot to mention that (my post was so long already!). It seems the cookies are not updated on the Preferences page until you reload it. Very unfortunate, but perhaps it's for performance reasons.