Lightweight, modern open-source CAPTCHA alternative designed using SHA-256 proof-of-work.



Cloudflare Turnstile is described as 'Turnstile is Cloudflare's smart CAPTCHA alternative. It automatically chooses from a rotating suite of non-intrusive browser challenges based on telemetry and client behavior exhibited during a session' and is an app. There are more than 10 alternatives to Cloudflare Turnstile for a variety of platforms, including Web-based, Self-Hosted, SaaS, Wordpress and Docker apps. The best Cloudflare Turnstile alternative is Cap Captcha, which is both free and Open Source. Other great apps like Cloudflare Turnstile are Anubis, reCAPTCHA, Procaptcha and Private Captcha.
Lightweight, modern open-source CAPTCHA alternative designed using SHA-256 proof-of-work.



Applies sha256 proof-of-work challenges to incoming HTTP requests, targeting AI crawlers, bots that ignore robots.txt, and automated scrapers, protecting server resources and preventing unwanted search engine indexing for privacy-focused sites.

reCAPTCHA is a free service that protects your site from spam and abuse, using risk analysis techniques to tell humans and bots apart.


Prosopo Procaptcha redefines user verification with a unique approach that emphasizes privacy and security. It's a pioneering solution designed to offer an alternative to conventional CAPTCHA systems that often compromise user privacy.





Private Captcha is an independent, privacy-first, self-hostable Proof-of-Work CAPTCHA service made in EU. Instead of asking users to solve complex puzzles or track their behavior, Private Captcha solves an invisible cryptographic task in the background.




Simple and self-hostable solution with full source available

hCaptcha is designed to solve the most labor intensive problem in machine learning: labeling massive amounts of data in a timely, affordable, and reliable way.



ALTCHA is a privacy-first solution built to help developers and website owners stop bots, spam, and automated abuse — without making things harder for real users. It replaces traditional CAPTCHA systems with a smarter, quieter approach to verification and threat detection.


mosparo is the modern solution for protecting your online forms from spam. The protection method is quite simple: mosparo blocks spam using rules matching the form’s data. The detection method is comparable to an e-mail spam filter.





In contrast to Cloudflare Turnstile, Friendly Captcha offers universal browser support and doesn't block users with older browser or devices. Cloudflare still requires user interaction with the Captcha whenever a user seems to be suspicious. That's not invisible at all, and an accessibility challenge.


TrustCaptcha is a privacy-first, invisible CAPTCHA that protects your website from bots and spam—without disrupting your users.




Turnstile was being easily bypassed by the various solvers available on GitHub. Procaptcha stopped these bots from getting through.