Despite the fact that HTTP is a stateless protocol, the headers, context and body are capable to persist among browsing sessions that is a core feature to track a visitor. This page demonstrates methods of tracking without using JavaScript.
Try to refresh this page several times, reopen the tab, reopen the browser and finally, open it in Private (Incognito) mode.
HTTP Cookie is a key-value pair set by the Web server and transmitted to the browser in the form of HTTP response header.
HTTP Etag is a token of a specific version of the resource and set by the Web server in the form of HTTP response header.
HTTP 301 Moved Permanently is a redirection instruction set by the Web server in the form of HTTP response.
HTTP Last-Modified is a timestamp of the resource set by the Web server in the form of HTTP response header. Since 01-01-101 may hold 60.5 billion uniques.
The demonstration may set pseudo-random online identifier. But don't worry! The identifier is not shared, used solely for this demo and will be removed in 5 minutes automatically.