cap — modern, lightning-quick PoW captcha

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

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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.