cap — modern, lightning-quick PoW captcha

Cap is the modern open-source ReCAPTCHA alternative designed for speed. FOSS, lightweight, private and secure.

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Note: This is still a work in progress. It should work in production but you might stumble upon unexpected errors.

Features

250x smaller than hCaptcha: Cap is lightning fast, so your pages load instantly and users don't wait around
Private & GDPR compliant: No more tracking or data collection. Cap is GDPR compliant and keeps your users' data private
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 PoW instead of frustrating image puzzles, making it easier and more private for humans
Headless mode: Need silent protection? Cap can run invisibly in the background without any user interface
Floating mode: The floating mode keeps your CAPTCHA hidden until it's needed, creating a smoother experience
Truly free: Completely open source under AGPL-3.0. No hidden costs, no premium features, no surprises and completely FOSS
Easy to integrate: Cap's web component & server-side library are super easy to integrate into your website

Why use this over Turnstile: Cloudflare Turnstile is known for having an extremely high error rate, especially for users using private browsers such as Brave or Librewolf. Also, Cap is open-source.
Why use this over RECAPTCHA: Cap is significantly smaller and faster than RECAPTCHA, open-source, fully free and doesn't require you checking traffic signs due to its PoW nature.
Why use this over hCAPTCHA: Not only is Cap's bundle 250x smaller than hCAPTCHA, it's open-source and doesn't require you checking traffic signs
Why use this over Altcha: Cap is slightly smaller than altcha and easier to integrate, but if you don't care about that and want a more mature solution I would highly recommend checking it out.
Why use this over FriendlyCaptcha: Unlike FriendlyCaptcha, Cap is free & open-source (FriendlyCaptcha is €39/month for 5,000 requests and 5 domains) and has a smaller footprint.
Why use this over MTCaptcha: Cap is more lightweight, doesn't rely on users solving an image puzzle that AIs like GPT-4o can solve, is open-source, more private and doesn't depend on third-party servers for verification.
Why use this over GeeTest: Cap doesn't require an account or API keys, has no usage limits, and is completely open-source with a simpler integration process. It also doesn't rely on slow, complex image-based puzzles that frustrate users