What are Cookies?

(explained in 5 minutes or less)

You’ve probably seen messages like this one:

So what does it mean? Well, cookies are simply small files sent to you by the website, and saved in your browser.

They allow websites to save information, like authentication data, your preferences (like a language you’ve selected), the last time you’ve visited a website, the items in your shopping cart — you get the idea.

Cookies are limited in size, so when developers need to save a lot of information — they can simply store your unique id in a cookie, and then just use it to access your data saved on their servers.

3rd party cookies and ad tracking

For security reasons, only the same website that saved information to your cookie can access it, but there’s a workaround to this rule.

Websites can embed bits of their code on other websites, by using ads, and that allows them to identify the cookie they’ve saved in your browser. Sometimes you can visit dozens of websites that have the same advertiser, and even though the websites themselves may store no information about you, the advertiser will be able to identify you and track your behavior.

That is why often ads may “follow” you across multiple websites, trying to show you the products you’ve clicked on before.

Just like any tool, cookies can be used for good or for evil, depending on the intent of the developer. If you like, you can look at the cookies the website stored about you by clicking Ctrl+Shift+I and going to the “Cookies” tab. You can always delete them or disable them completely in your browser’s preferences.