google 人机身份验证

Are you a robot? Introducing “No CAPTCHA reCAPTCHA”

https://googleonlinesecurity.blogspot.com/2014/12/are-you-robot-introducing-no-captcha.html

reCAPTCHA     google 人机身份验证

Protect your website from spam and abuse while letting real people pass through with ease.

Tough on bots   ，Easy on humans。

示例图片：

1  demo

https://www.google.com/recaptcha/api2/demo

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参考链接：

https://www.google.com/recaptcha/admin#list

https://www.google.com/recaptcha/intro/index.html
https://www.google.com/intl/zh-CN/policies/terms/
https://www.google.com/intl/en-US/policies/terms/
https://en.wikipedia.org/wiki/ReCAPTCHA
https://zh.wikipedia.org/wiki/ReCAPTCHA

其他参考链接：

https://github.com/google/recaptcha
https://wordpress.org/plugins/wp-recaptcha/
https://wordpress.org/support/register.php
https://www.drupal.org/project/recaptcha
http://contactform7.com/recaptcha/

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