Product Information
What is Cap-4?
Cap is a fast, lightweight, and modern open-source alternative to CAPTCHAs, based on SHA-256 proof-of-work (PoW). It is 250 times smaller than hCaptcha, privacy-centric, fully customizable, and easy to self-host. Cap helps prevent spam and abuse without tracking users, making it ideal for privacy-conscious developers. Built for speed and simplicity, Cap is perfect for modern web applications, forms, and APIs that require secure, lightweight human verification.
How to use Cap-4?
Cap is a lightweight, open-source SHA-256 proof-of-work alternative to CAPTCHA, designed to help modern web applications, forms, and APIs perform secure, lightweight human verification while protecting user privacy.
Core Functions of Cap-4
Based on SHA-256 proof of work
Minimal widget library size (approx. 20kb)
Protect user privacy, no tracking
Fully customizable and supports self-hosting
Supports invisible and floating verification modes
Provide a Cloudflare-like browser checkpoint experience
Usage Scenarios of Cap-4
- Prevent website spam and abuse
- Human verification for modern web applications
- Protect form submissions and API endpoints
- Suitable for privacy-focused scenarios
Common Questions about Cap-4
What does Cap do?
How do I use Cap?
What are the core features of Cap?
What are the use cases for Cap?
