Good potential but... Rated 4 out of 5 stars

This extension has a good potential in terms of privacy and maybe in
performance but, in my opinion, it works with a wrong logic, which makes
it to have no effect in a specific browsing manner.
It deletes the cookies on a per tab basis and not per website or domain.
However, some users may visit many different websites through the same
tab, by clicking on links, opening bookmarks etc.
Even worst, this tab may survive for many days if the user has the habit
to save and restore the session.
SDC will delete the cookies altogether only if this tab is closed.
Otherwise, the user will become soon the proud owner of a huge
collection of cookies!
There is also some other issue, maybe intentionally by design but, i
consider this is a problem, since there is no option for the user to choose
the preferable behavior.
I have set FFx to keep the cookies until i close it, so, every time i restore
the saved session, my tabs are as i left them but the list of cookies is
empty (for performance on start-up reasons, the selected tab when i
close FFx/save session is a new tab).
SDC bypasses FFx's default behavior, causing it to retain the cookies of
all restored tabs, if they have visited in a previous session but after the
installation of SDC.
Therefore, should be an option in extension's preferences for the user to
select the preferable behavior.
I mean the behavior which applies to all websites by default because, it's
not convenient for the user to have all the time in mind to click on SDC's
icon for every website and select what SDC to do for the specific site.
These options in SDC icon's menu are useful when the user just wants to
set an exception for some websites which are the minority.


Hi Ove,
Thank you very much for response.
After your explanations, i understand your position and tend to agree but i
still have some concerns..
Your example about a transaction via Paypal is very clear and good.
However, about how deep is a tab's history (and therefore the collected
cookies) respected by SDC, you should not forget that the modern
machines, especially these with 64bit OS's, have (or may have) huge amount
of RAM and therefor, FFx may retain a very large size of back-forward cache
I have noticed that my FFx, with a few tabs and after a while of browsing,
can easily reserve 1-1,5 Gigs of ram or even more.
Therefore, my opinion for an improvement of SDC, is the possibility for the
user to adjust in extension's preferences the deep of tab's history in terms of
cookies. I mean the number of most recently visited main domains for which
SDC will keep their cookies until the tab is closed, while the older will be
discarded (rather than a on/off option to disable or not the bfcache).

About the second issue, i'm afraid i was not so clear..
If you set for cookies "Keep until: I close Firefox", then Firefox will clear the
list on shutdown, regardless if there are some tabs left open (session to be
SDC changes this behavior of FFx.
You told me "if you would like Firefox to delete a site's cookies on shutdown,
you just mark it yellow" but, as i already mentioned, it's not convenient for
the user to have all the time in mind to click on SDC's icon for every visited
website and mark it yellow.
Also, i haven't marked any domain as green!
Why to do it since i want all cookies to be deleted on FFx's shutdown?
In other words, SDC should not modify FFx's original functionality or you
could make it optional. Now, with SDC installed, the user setting "Keep until:
I close Firefox" has no effect.

There is also another issue as i noticed.
I make use of "Yahoo! Mail Notifier". Upon Firefox startup, this extension
checks for new mail and after that, continues to do so periodically (in the
After i installed SDC, this behavior has been affected too.
Upon Firefox startup, if i delay to click on YMN's icon more than SDC's
default timeframe (10 secs, i have increase it now), SDC deletes Yahoo!'s
cookies and this leads me to Yahoo!'s login page instead of my inbox!
If i click on YMN's icon within SDC's timeframe, i go to my inbox but after i
close Yahoo!'s tab, YMN cannot any more continue to check periodicaly for
new mail, because in the mean time SDC has deleted Yahoo!'s cookies!
YMN appears always as not connected and i have to manually click on its
icon to check for new mail.
For now, i keep Yahoo!'s tab always open during my browsing session, to
"protect" its cookies.
As you can realize, there are also many other similar cases/scenarios, like
the above.

Of course, i know that i could mark green Yahoo!'s cookies but doing so, SDC
loses its main purpose of privacy protection.
Ideal condition for SDC would be if it's possible to mark green only specific
cookies of a website. E.g., only Yahoo!'s login cookie(s) in the above scenario.
As i noticed, technically it's possible to maintain the login status with only
two cookies of the many set by Yahoo! because, making an experiment, i
delete manually Yahoo!'s cookies one-by-one and try to visit Yahoo mail until i
got the two cookies of interest (login status). Maybe one more cookie is
needed for the login procedure.

Microsoft's mail sets far more cookies at all..
Currently SDC can only keep or delete all the cookies of a website,
regardless of the purpose of each one.

So, could you make SDC to be more "discrete"..? :)


This review is for a previous version of the add-on ( 

Update: Thank you for clarifying. If you haven't added "green" whitelist entries, SDC should not impact your "Keep until: I close Firefox" setting. Mail me at and we can try to find out what's going on. This is not the expected behaviour.

Thank you for your comprehensive feedback.SDC keeps the cookies for a certain number of sites in the history of the current tab. They will eventually self-destruct, even if you do not close the tab. It just takes a little time. This is by design and to improve usability in two scenarios:1. When you navigate away from a page within the same tab, the old page is not really unloaded. Firefox just hides it and puts it in its "bfcache". When you use the back-button to return to such a page, its state will be restored directly from this bfcache. Nowadays a lot of websites are really rich applications in their own right (think Gmail) and not static html documents. If SDC were to remove cookies from such a page in your bfcache and the user used the back button, problems are bound to happen. We would find ourselves in a situation, where the application state was restored from a time when the cookies were present, but are now no longer accessible. This is an unexpected situation for the webapp and it might break in unexpected ways. That's why SDC keeps cookies for sites that are still in your bfcache. Firefox determines the size of this cache depending on the available RAM by default.2. Additionally, SDC will - in general, except for cases where it detects that somebody tried to sneak in a cookie via redirect tricks - keep cookies for the last three prior domains (not pages) that were active in the open tab. This is to ensure that inter-domain transactions work. Think of a shop forwarding you to Paypal and back.If you keep using the tab (and actually visit a few different domains) you will find that the old pages' cookies do eventually expire. How long this will take, depends on the size of your bfcache. I might add the option to disable all this in a future version, but be aware of the side-effects.Regarding clearing cookies on shutdown: I also consider this a feature not a bug. As you have experienced, SDC and Firefox share the same cookie whitelist. If you mark a site "green" in SDC, Firefox will also honor this exception. Because both SDC and Firefox interpret these entries in the same way, it seemed unneccesary to introduce a second place to manage them. The fix for your problem is really simple: if you would like Firefox to delete a site's cookies on shutdown, you just mark it yellow ("after you close the browser") in SDC and not green ("never"). If you would like all of your cookies to be cleared when you close the browser, just don't mark anything "green".