Cap is a lightweight, modern open-source CAPTCHA alternative using proof-of-work and instrumentation challenges. It's fast, private, and extremely simple to integrate.
Read the docs , try the demo or deploy on Railway
Cap replaces visual captchas with modern, accessible and privacy-preserving challenges. No images, no tracking, no dependencies, works everywhere.
The default way to use Cap is with the Standalone Docker container. Learn more about how Cap works
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250x smaller than hCaptcha
~20kb, zero dependencies, loads in milliseconds -
Privacy-first
Cap doesn't send any telemetry back to our servers -
Fully customizable
Change the colors, size, position, icons and more with CSS variables -
Proof-of-work
Your users no longer have to waste time solving visual puzzles. -
Standalone mode
Run Cap anywhere with a Docker container with analytics & more -
No user interaction needed
Hide Cap's widget and solve challenges in the background -
Open-source
Completely free & open-source under the Apache 2.0 license
Cap is a great alternative to reCAPTCHA, hCaptcha and Cloudflare Turnstile
This project is licensed under the Apache-2.0 License, please see the LICENSE file for details.
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