I'm currently experiencing the same problem. Using the Visitor Group Statistics gadget on the dashboard also shows no hits for the visitor group using this criterion.

Same here, seems that this  very basic criteria does not work, we are running 9.12 version. Didn't find any bug from bug list related to this. Others, any news?

Hi, we still get this problem. Using EpiServer.CMS 11.20. Does anyone know if this was ever fixed?

I also have this problem. CMS 11.9.2.0

I've used that criterion successfully and can confirm that it does work however there are some caveats to be aware of. The referrer which is used by the referrer criterion is the value of the referrer header in the first request received by the site in a given session, not the referrer from the current request. In the original post, the first step in the reproduction steps is to visit the alloy site directly. Because it's being hit directly, there will be no referrer so, even though the last step says to hit the alloy site from a link on twitter, that referrer on the request from Twitter will be ignored because it's not the first request to the site.

You should also bear in mind that the referrer header isn't always present and, even if it is present, it may not contain what you think it should. In the original post, the alloy site runs on HTTP and twitter runs on HTTPS. That's relevant because of browsers' referrer policies. The current default policy on Chrome (strict-origin-when-cross-origin) means that, if you're linking to a less secure site (e.g. HTTPS to HTTP), no referrer header will be sent. If you're linking from one HTTPS site to another, there will be a referrer header but it will contain the site origin rather than the whole URL.