Understanding CAPTCHAs: History, Types, Implementation, and Future Trends
Introduction CAPTCHA—an acronym for Completely Automated Public Turing test to tell Computers and Humans Apart—has become a ubiquitous part of the modern web. From comment sections and sign‑up forms to ticketing systems and online banking, CAPTCHAs serve as the first line of defense against automated abuse. Yet despite their prevalence, many developers and security professionals still have only a surface‑level understanding of how CAPTCHAs work, why they exist, and where the technology is heading. ...