What is a cookie?
In one sentence: A small note a website asks your browser to keep and send back on later visits. Useful for logins; also used for tracking. This site sets none.
A little more
Web servers forget you between requests. A cookie fixes that: the server asks your browser to remember a short note (often a random ID) and send it back with every later request. That's how a site keeps you logged in or remembers what's in your basket.
Cookies from other companies embedded in a page (third-party cookies) can follow you across many sites, which is why browsers now block or limit them. You can see and delete cookies in your browser's settings.
It's a bit like… A cloakroom ticket: the server keeps your coat, you keep the ticket, and showing it later proves which coat is yours.
See it in action
- 1What happens when you open a web page?Follow one click from your keyboard to a server and back: DNS, the padlock handshake, HTTP, tunnels and painting the page.6 min · interactive
- 2Anatomy of a web addressPaste any web address and see it taken apart, colour by colour: scheme, host, port, path, query and the fragment that never reaches the server.5 min · interactive
- 18What is a cookie on a website?Fill a pretend browser's cookie jar: see how a website remembers your basket and login, what session cookies are and what closing the browser throws away.7 min · interactive