You may not know it, but you've been using magic cookies your entire life. Magic cookies are the invisible tokens of data exchanged from a server to a client that is used to track, authenticate and inform the client in the system about the presence of the server. They differ from regular data packets because they don't contain readable data, only path information through which the server can be reached. You might have seen them if you visited the last updated website years ago. You'll notice that some sites will load just fine, while others take an eternity to load and spit out an error message when they finally do load. This is because some old websites have expired magic cookies, so when you try to access them, it takes forever for your browser to figure out where it needs to send all of its requests for resources like images and scripts. Cookies: the sweetest way to track your users. Cookies are bits of code that websites use to keep track of you as you move around the internet. They can be used for many things, from remembering your log in info to keeping track of which ads you've seen and which are most effective. The most common types of cookie are HTTP, which is used on web pages and can only be read by the server hosting them. They're encrypted and unreadable under normal circumstances and generated by the server that set them up in the first place. Third parties can also set HTTP cookies (like Google Analytics or Facebook), which are used to track user information across multiple sites. It is helpful for advertisers who want to ensure their ads are working correctly. Still, it can also lead to pretty creepy data collection uses—like figuring out how much time people spend on certain parts of a site so they can focus their advertising efforts there!