Cap

In plain words

Cap is an open-source CAPTCHA alternative that uses SHA-256 proof-of-work verification instead of traditional image recognition. Significantly smaller than competing solutions, it prioritizes privacy and customization while remaining fully invisible to users. Built with JavaScript instrumentation and available as free and open-source software, Cap is designed for developers seeking a lightweight, privacy-focused security option for their applications.

written from the facts on this page · September 2026

From the sources

Cap is a lightweight, modern open-source CAPTCHA alternative designed using SHA-256 proof-of-work and JS instrumentation. It's: - ⚡️ 250x smaller than hCaptcha - 🔒️ Private - 🌈 Fully customizable - 🤖 PoW-based - 🌳 Fully FOSS - 💨 Invisible

Cap is a free, open-source CAPTCHA alternative. Self-hosted, privacy-first, no Google. Proof-of-work and instrumentation, no visual puzzles. Apache 2.0.

No Google. No telemetry. No visual puzzles. Switch from reCAPTCHA in minutes. Zero telemetry. No third-party network. Your users' data stays between you and them. ~20kb, zero dependencies. Loads in milliseconds, not seconds. PoW, time-lock challenges and instrumentation run silently in the background. Apache 2.0 licensed. Audit it, fork it, self-host it. No vendor can pull the rug. Designed to help you meet GDPR, CCPA, LGPD and more, with strict privacy and accessibility standards baked in. Colors, size, position, icons, all controllable via CSS variables. No iframe lock-in. Cap's widget is extremely lightweight and runs invisibly, shipping only about 20 kB of JavaScript with no third-party…from capjs.js.org

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  I built Nocaptcha after getting frustrated with traditional CAPTCHAs both as a user and developer. WebAuthn passkeys offered a promising alternative that's both more secure and user-friendly. What makes Nocaptcha different: - Uses WebAuthn standard instead of puzzle-solving - No need for users to remember passwords or solve puzzles - Open source Current limitation: Working with W3C WebAuthn Community Group on true passkey disposal for this use case. Looking for feedback particularly on: 1. Integration experience 2. User experience compared to traditional CAPTCHAs

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• RC
  Replace CAPTCHA with Proof-of-Work2014 · hashcash.io · ▲89

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