A web cookie (also known as an HTTP cookie) is a tiny snippet of data that gets added to the user’s web browser when they visit a certain website. The code is stored in the user’s browser over a period of time set by its creators (or until the user deletes it), and changes the way the browser interacts with certain pages. This technology is used to facilitate various functions, including: activating retargeting ads – more on that later; storing stateful data (e.g. the items you’ve added to your shopping cart on an ecommerce site); retaining data previously entered into forms (used for autocomplete functions); saving user preferences; authentication cookies communicate the user’s account details and log-in status to account-protected servers; recording user activity.