Cap

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.

Documentation

Read the docs, try the demo or deploy on Railway

What is Cap?

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

Why Cap?

• 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

License

This project is licensed under the Apache-2.0 License, please see the LICENSE file for details.

Copyright ©2025 - present tiago

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