Google recaptcha remoteip explanation
问题 In the documentation of recaptcha it says that the remoteip argument is optional, but I don't understand its purpose, because even if I send a different IP than REMOTE_ADDR, the response from Google is still a valid captcha. 回答1: It is already asked in Information Security and I will provide the accepted answer here, too. Because it is not clear that it is mainly a security issue: Because there could be a DNS/hosts reroute in place to allow the captcha to be parsed differently by a malicious