dereferer

A  dereferer  is a (commonly server-side) script that prevents a linked website to see what page the link was clicked on by either replacing or removing the |HTTP referer. The technique is commonly used to keep internal URLs private or to prevent sensitive data to leak into other server's log files (e.g. outgoing links from e-mail applications etc.)

For details on when HTTP referers are sent and common workarounds, see https://en.wikipedia.org/wiki/HTTP_referer#Referer_hiding

W3C-recommended solution
With up-to-date browsers, this can be achieved by setting a |Referrer Policy on
 * HTTP header
 * meta element
 * referrerpolicy content attribute on an a, area, img, iframe, or link element
 * noreferrer link relation on an a, area, or link element
 * implicitly, via inheritance

Script implementations

 * JS solution: https://stackoverflow.com/questions/8893269/what-is-the-most-reliable-way-to-hide-spoof-the-referrer-in-javascript/8957778#8957778
 * PHP solutions commonly involve linking first to a "dereferer" URL which then forwards the user to the final target (in consequence, URLs in the HTML do not contain their real destination URL)

3rd party services
Third-party services providing link redirection to obscure the referer:
 * https://dereferer.me/
 * http://www.dereferer.de/