Originally Posted by
anon
Cookies expire either on a preset date, or upon closing the browser if no date is set. The only way for a site to "delete" a cookie is to set said date in the past, effectively (and immediately) killing it. If you have an old browser profile backup, you can temporarily turn back your system clock, and be able to retrieve their names and values.
Anyway, there are lots of cookie editing addons for all major browsers. The developer console will always offer at least basic capabilities. If you know how to use JavaScript, you can do it yourself through the document.cookie object (but will not be able to interact with HttpOnly cookies).
Even though Netscape Navigator is long gone, its cookies.txt format remains relevant, so I recommend becoming familiar with it too.