Nginx : Block User Agent

In Nginx, you can block certain user agents (normally it is crawler) like this :

server {
  listen          80;
  server_name     mysite.com;
  root            /etc/tomcat7/webapps/mysite;
  if ($http_user_agent ~* (ahrefs|wget|crawler|majestic) ) {
    return 403;
  location / {
        <!-- xxx -->

In above example, for “user agent” that contains one of this pattern : ahrefs|wget|crawler|majestic, HTTP 403 will be returned.