When web browsers navigate to web pages they send a HTTP referrer header telling the destination web page what the source web page was. If you don't want the destination web page to know what the source was you need to use a meta-refresh redirection facility such as meta-refresh.me which uses the HTML meta refresh facility to process the redirection which avoids the referrer HTTP header. Simply submit the desired destination URL and a private redirection URL will be generated which you can use for private redirection.
Include the following HTML for private redirection:
<script type="text/javascript" src="https://meta-refresh.me/api/1.0/auto.js"></script>