Best Free CAPTCHA Software

ALTCHA is a modern security and privacy-focused platform built to defend web services from bots and abuse — without compromising the user experience. At the heart of its ecosystem is ALTCHA Sentinel, a next-generation threat detection and mitigation system designed to protect websites, APIs, and applications from automated attacks, spam, and other forms of abuse. ALTCHA Sentinel stands out by combining adaptive machine learning, behavioral analysis, and smart verification techniques. It doesn’t rely on intrusive CAPTCHAs or outdated blocking tactics; instead, it works invisibly behind the scenes, analyzing traffic patterns in real time to identify and stop threats before they cause harm. Sentinel protects critical entry points like sign-up forms, login pages, and comment sections — all while keeping the experience seamless for real users.

Dynamic & PoW CAPTCHA: Real-Time Bot & Cyber Threat Defense | Prosopo Procaptcha Prosopo Procaptcha provides comprehensive protection against various automated threats, including web scraping, credential stuffing, account takeover attempts, clicks fraud, distributed denial of service (DDoS) attacks, inventory hoarding, credit card fraud, and other forms of malicious bot activity that can harm your online business or compromise user data. With no hidden fees and transparent pricing, our solution provides an affordable alternative to expensive services like reCAPTCHA and hCaptcha. Procaptcha dynamically evaluates user interactions by analyzing browser environments and behavior. Based on risk scores, it automatically applies the appropriate challenge, making it difficult for bots to bypass while ensuring a smooth experience for real users.