How do I remove a cookie that I've set on someone's computer?

Question

I've got a web system where users log in, and it stores a cookie of their session. When they log in as someone else or log out I want to remove that original cookie that I stored. What's the best way to do that? I'm using Python and Apache, though I suppose the answer will remain the same for most languages.

Answer 1

I guess the best way is to set the expiration to a date of the cookie to some date in the past.

Answer 2

Set the cookie again, as if you hadn't set it the first time, but specify an expiration date that is in the past.

Answer 3

Return the header

Set-Cookie: token=opaque; Domain=.your.domain; Expires=Thu, 01-Jan-1970 00:00:10 GMT; Path=/ 

The Domain and Path must match the original attributes that the cookie was issued under.