A cookie (also known as a web cookie or browser cookie) is a small piece of data a server sends to a user's web browser. The browser may store cookies, create new cookies, modify existing ones, and send them back to the same server with later requests. Cookies enable web applications to store limited amounts of data and remember state information; by default the HTTP protocol is stateless.| MDN Web Docs
Enhanced Tracking Protection (ETP) has been expanded to block a particularly invasive form of cross-site tracking: browser fingerprinting. This is the practice of identifying a user by the unique characteristics of their browser and device.| Mozilla Security Blog
