ELI5: how cookies work

// eli5

What are internet cookies?

Cookies are like tiny sticky notes that websites put on your computer to remember information about you [2][4]. When you visit a website, it writes down things like your favorite color or that you're logged in, and saves this information in a small file [4].

Why do websites use cookies?

Websites use cookies so they don't have to ask you the same questions over and over again [3]. Instead of asking "Who are you?" every time you visit, the website can read the sticky note it left behind and say "Oh, welcome back! I remember you!" [2][5].

What happens when you visit a website again?

When you go back to a website, your browser automatically sends those tiny sticky notes back to the website [1][5]. The website reads them and remembers your preferences, like if you like dark mode or what items are in your shopping cart [2][4].

Can cookies be dangerous?

Cookies themselves are just information, but some websites might use them to track where else you go on the internet [3][4]. That's why you sometimes see ads following you around online!