Open Source Alternatives to Cloudflare Turnstile
A bot mitigation widget that provides invisible CAPTCHA challenges for websites, allowing users to verify they are human without friction, while protecting sites from automated abuse and spam.
Whether you want to cut software costs or escape vendor lock-in, these open source alternatives to Cloudflare Turnstile give you an option you fully own. You can self-host them, so your data stays on infrastructure you control. This page lists 3 open source alternatives to Cloudflare Turnstile. The most popular are Cap, ALTCHA and mCaptcha. Most use the AGPL-3.0 or Apache-2.0 license, and 3 offer an official Docker image.
Cap
A lightweight bot protection system using proof-of-work and instrumentation challenges to replace visual puzzles and tracking.
ALTCHA
A self-hosted spam protection system using proof-of-work mechanisms to replace traditional visual CAPTCHA puzzles.
mCaptcha
A privacy respecting proof of work system that protects websites from bots without requiring image solving.
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