ALTCHA: Lightweight, Privacy-Preserving Anti-Spam Solution

ALTCHA is a self-hosted anti-spam service for websites and APIs. It uses a proof-of-work mechanism instead of CAPTCHAs, protecting user privacy and complying with GDPR and WCAG 2.2 AA standards. ALTCHA is lightweight, cookie-free, and fully accessible, offering a SaaS API and extensive configuration options including custom requests, spam filtering, and data obfuscation. Its size is a mere 6% of reCAPTCHA.