Everyone who is reading this article would have come across captcha validation while doing registration in a website or sometimes by other means. Some websites put a captcha validation in place to get rid of spammers. An application can either be accessed by human being or by a client program. Yes Of course! There is possibility that an Http client program developed by a professional hacker can access your application. In order to fill this security hole we can implement a captcha validation because a program can't read captcha image. Therefore, as a developer, you should have knowledge of 'How to secure Spring Boot Application by Captcha Validation?'. More or less, we will learn to implement spring boot captcha.