just what does emptying cookies actually do?

Answer 1

Cookies remember things, so for sites where you ticked "Remember me", or "Remember password", they will no longer remember.
Also, things like auto-populating bank accounts, addresses, email addresses etc will be a bit hit-and miss afterwards.

Answer 2

There are several types of cookies which perform various tasks.

The most common of these are called C-Cookies and they take information that you have already filled into your browser in forms and save it to your local machine rather than to a server. This way your machine "remembers" who you are and when you return to that site gives you the option to recall that information to make your life simplar by filling in certain fields for your or having sections that appear to identify you by name such as your bank account greeting you with your name before you even login.

B-Cookies are tracking tools similar to spyware but without doing harm to your PC. These trackers track your movements to and from the host site to find out how you were referred to a site and when you went afterwards. The host company then collates this data to get an idea of how users use a website.

Emptying cookies just clears the information in C-cookies so that you will have to fill in a lot of fields from scratch again. It also clears B-cookies which gives host websites a lot of problems understanding if you are a new user to a site, how many times you have been there in the past and how many pages you may have viewed in the course of the day.

For this reason there are some companies that will pay you to keep all of your cookies to measure your movements accross the web then sell this information onto larger websites and marketing companies for a healthy profit.

Such companies are Hitwise and Comscore.


In addition to this emptying your cookies can free up a very small amount of space on your PC and speed up your browser as it does not have to trawl through cookies to retrieve any information if the information is not there.

Answer 3

cookies are small files (typically less than 0.5 kilobytes) that are stored on your computer. Typically they contain a text string that identifies you as a particular user to the server. The server can ask your computer to write a cookie or read the contents back to it.

When you "empty the cookie jar" or "empty the cookies" your computer simply deletes all these files.

People used to be scared about what might be stored in cookies. Some (really lame) websites store login details and other sensitive information but that is now fortunately quite rare. Many websites now give a different "look and feel" depending on the contents of the cookie and when you delete them you get the "new user" interface (e.g. eBay).