AGPL-3.0

Gesture Dynamics CAPTCHA Emerges as Privacy-Focused Drop-in Alternative to reCAPTCHA

A new open-source CAPTCHA system called Aptogon replaces traditional image-based challenges with analysis of hand gesture dynamics to verify human users. Instead of clicking on traffic lights or buses, visitors draw a free-form gesture for about ten seconds while the system measures velocity variance, pause entropy, rhythm irregularity, and micro-corrections that distinguish human motor patterns from bots. The solution addresses recent reCAPTCHA restrictions, including Google's reduction of free monthly verifications from one million to ten thousand and tightened GDPR data responsibility rules starting in April 2026. An iframe architecture loaded from the vendor origin eliminates cross-origin issues and CORS blocks while supporting public and secret key pairs for domain validation. Machine learning relies on a local gradient boosting model for confident decisions and an LLM only for borderline cases, with fail-closed behavior returning 503 errors when the classifier is unavailable. Coordinates never leave the browser; only derived statistics are sent, satisfying GDPR requirements without cookie banners or biometric templates. The project is released under AGPL-3.0 with a free tier of one thousand checks per month and integration examples for HTML, React, Node, Python, and PHP.