Another, similar, technique is checking for a NOBOT cookie and if it doesn't exist, serve up a page that uses javascript to set the cookie, then reloads. This

Another, similar, technique is checking for a NOBOT cookie and if it doesn't exist, serve up a page that uses javascript to set the cookie, then reloads. This requires the bot to interpret javascript, and it can easily be configured in nginx and other load balancers.