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Cap logo

cap — modern, lightning-quick PoW captcha

Cap is a lightweight, modern open-source CAPTCHA alternative designed using SHA-256 PoW.

Learn more

npm @cap.js/server npm @cap.js/widget OpenSSF Best Practices

Cap captcha

Why Cap?

  • 250x smaller than hCaptcha
    Cap's widget library is extremely small, only 12kb minified and brotli'd.
  • 🔒 Private
    Cap's usage of proof-of-work eliminates the need for any tracking, fingerprinting or data collection.
  • 🌈 Fully customizable
    Cap is self-hostable so you can customize both the backend & frontend — or you can just use CSS variables
  • 🤖 PoW-based
    Cap uses proof-of-work instead of complex puzzles, making it easier for humans and harder for bots
  • 🧩 Standalone mode
    Cap offers a standalone mode with Docker, allowing you to use it with languages other than JS.
  • 💨 Invisible mode
    Cap can run invisibly in the background using a simple JS API.
  • ☁️ Floating mode
    Floating mode keeps your CAPTCHA hidden until it's needed
  • 🌳 Fully FOSS
    Completely open source under AGPL-3.0, with no premium versions.

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Description
The privacy-first, self-hosted CAPTCHA for the modern web.
Readme 10 MiB
Languages
JavaScript 95.8%
CSS 3.1%
Rust 1.1%