What are Browser Cookies and How Are They Used?

Browser cookies are a simple and powerful way websites can leave information on your computer to use when you return. In recent years, we’ve seen an increase in the number of sites that include a “This site uses cookies, is that OK? ” kind of warning in response to regulations imposed by various countries.

Cookies are simply data a website asks your web browser to place on your computer. The next time you visit that same site, the web browser automatically sends any cookies it previously saved for that site. The cookie left previously is provided each time you re-visit the same site. Whether the site does anything with that cookie is entirely up to the site.

It’s called a cookie because it doesn’t have to be anything specific. Cookie is just a generic term here for “data”. That data could be a yes/no flag that you’ve visited the site before, or a number that somehow identifies you to that site, or just about anything else the site-designer wants it to be.

A simple example is a site where you need to log in. A cookie might be used to “remember ” your log-in name if you want it to.Th e first time you visit the site, you type in your log-in name and password and perhaps click a checkbox labelled “Remember me”. Once the login is successful, the site puts a cookie on your machine saying (for instance) “username=Leo”. The next time you visit that site, that cookie is automatically sent, so the site “knows” you’re Leo and fills in the username field for you.

Not just anyone can see every cookie. Cookies associated with one website cannot be read by any other site. It’s important to realize that cookies only contain information placed there by the websites they’re associated with. That means they can only contain information the site already knows. A site might know your name, and display it in subsequent visits, but only because you told it your name during the previous visit. Cookies are nothing more than a way for websites to remember something — anything they choose to remember —fro m visit to visit.

Cookies in and of themselves are nothing to be concerned about. They enable a tremendous amount of functionality on the web. If you were to disable cookies completely, you’d quickly find that much of the web simply wouldn’t work or would at least become exceptionally inconvenient.

Source: Adapted from “Ask Leo (May 252018)” in  S e n i o r N e t M a r l b o r o u g h S o u n d s  newsletter