Open Source CAPTCHA & Bot Protection Tools using CSS
A curated collection of the best open source tools for distinguishing humans from bots (CAPTCHA) and preventing spam. using CSS.
Privacy-first CAPTCHA alternative with proof-of-work
Stars
Stars growing over the last 30 days8,105Last commit
8 days agoLicense
Apache-2.0
Lightweight open-source CAPTCHA solution using SHA-256 proof-of-work. 250x smaller than hCaptcha, fully customizable, and privacy-focused with zero telemetry.
Open Source Alternative to:
Next-Gen CAPTCHA and Spam Protection, GDPR compliant
Stars
2,834Last commit
2 days agoLicense
MIT
ALTCHA offers cutting-edge spam and abuse protection for websites and apps, with privacy-friendly CAPTCHA alternatives designed for GDPR compliance.
Open Source Alternative to:
Privacy-first proof-of-work CAPTCHA without user friction
Stars
2,494Last commit
1 year agoLicense
AGPL-3.0
Privacy-focused proof-of-work CAPTCHA system that silently protects websites without tracking users or requiring image solving. Drop-in replacement for reCAPTCHA.
Open Source Alternative to:
Decentralized CAPTCHA for enhanced web security
Stars
304Last commit
6 hours agoLicense
Apache-2.0
A blockchain-based CAPTCHA solution offering improved security, user experience, and resistance to bot attacks for web applications.
Open Source Alternative to:
GDPR-compliant bot protection without user friction
Stars
198Last commit
6 hours agoLicense
Unknown
Privacy-first CAPTCHA service that blocks bots while keeping forms accessible. No puzzles, no tracking, no cookies - just invisible cryptographic protection.
Open Source Alternative to:
c15t – Open-source cookie banner, built for control and lightening fast modern web apps.
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