Where does Firefox store cookies in Linux? I searched everywhere but did not find anything.
Firefox stores cookies in sqlite database
~/.mozilla/firefox/<profile path>/cookies.sqlite. You can have full access to it.
For example, to watch all cookies from stackoverflow.com you can do:
cd ~/.mozilla/firefox/<profile path>/ sqlite3 cookies.sqlite select * from moz_cookies where baseDomain glob '*stackoverflow*'
<profile path> by path of your firefox profile).
To see names of database fields do:
If you need a text file with the cookie information, you can dump all your cookies using different add-ons.
When I needed cookies for downloading using wget, I dumped using Export Cookies and then loaded them in wget using
wget --load-cookies <cookiefile>
Others have provided great detail. I would just like to add to the discussion that you can search through your cookies (and optionally remove them) by going into "Open Menu">Preferences>Privacy>"remove individual cookies" link.
For all intensive purposes, using the sqlite method provided to browse through the cookies database is of course far superior, as it is a database and you can use SQL statements on the data.