CAPTCHA
A challenge–response test used to tell humans and bots apart, such as identifying images or checking a box, to block automated access.
Full Definition
CAPTCHA stands for Completely Automated Public Turing test to tell Computers and Humans Apart. It presents challenges that are easy for humans but difficult for bots: clicking fire hydrants in a grid, solving audio puzzles, or simply clicking an "I'm not a robot" checkbox (which uses invisible risk analysis behind the scenes). Modern CAPTCHAs like reCAPTCHA v3 score traffic continuously based on behaviour and only trigger visible challenges for suspicious sessions. For scrapers, CAPTCHAs can be solved by third-party solving services (2Captcha, CapSolver) or by using high-trust residential proxies to avoid triggering them in the first place.
