Hi, I add this in user.filter, CLIENT-HEADER-TAGGER: mytest Test s/.*hel.*/MYTAG/ and this in user.action, {+client-header-tagger{mytest}} {+block{bl}} TAG:MYTAG I test it with command curl -v -H "User-Agent: hello" -x http://127.0.0.1:8118 www.bing.com but it does not work. Privoxy version is 3.0.26. Thanks.