Rated 5 out of 5 stars
I remember a similar addon that has long since abandoned. Thank you for creating a new version. It's so simple to use.
I tested it by doing a google search for ipswift then clicking the ipswift top result since that site lists your Referer. I had the addon set for zero, and the result for "HTTP Referer" was "none". So your addon appears to work as advertised.