%HTTP%
%HTTP{"Header-name"}%
%HTTP% | |
%HTTP{"Accept-language"}% | en-US,en;q=0.5 |
%HTTP{"User-Agent"}% | CCBot/2.0 (https://commoncrawl.org/faq/) |
You can see the HTTP headers your browser sends to the server on a number of sites e.g. http://www.ericgiguere.com/tools/http-header-viewer.html