Get Started with ALTCHA

Tip

ALTCHA Widget v3 is now available. This documentation reflects the latest version, including updates to the widget API and an improved Proof-of-Work (PoW) system.

ALTCHA (“Alternative CAPTCHA”) provides a modern, privacy-focused alternative to reCAPTCHA and other legacy CAPTCHA systems. Instead of relying on intrusive tracking, it uses a proof-of-work mechanism, along with advanced threat detection methods when integrated with ALTCHA Sentinel.

ALTCHA is fully self-hosted, ensuring strong data privacy and compliance with modern regulatory standards.

Why ALTCHA?

• Frictionless experience for most users (no interaction required)
• Effectively blocks advanced bots and abuse
• Privacy-focused: no cookies, no tracking, and GDPR-compliant
• Accessible and WCAG-compliant
• Open-source core for transparency and control
• Lightweight and fast-loading for optimal performance
• Flexible, with developer-friendly integration
• Enhanced protection when combined with ALTCHA Sentinel

Components

A complete implementation includes three parts:

1. ALTCHA Widget - JavaScript component that handles proof-of-work verification and user interaction with customizable UI options and lightweight implementation.
2. ALTCHA Sentinel - Self-hosted all-in-one spam protection platform that combines proof-of-work with machine learning and pattern recognition to block abuse while maintaining full privacy compliance. Recommended for production environments requiring robust protection.
3. Integration libraries - Server-side tools for payload validation and verification, supporting multiple programming languages.

Recommended Setup with ALTCHA Sentinel

For full protection and compliance:

1. Install ALTCHA Sentinel on your infrastructure
2. Embed the JavaScript Widget in your website
3. Validate submissions with the server libraries

Open Source Option

For basic proof-of-work protection without ALTCHA Sentinel:

1. Set up server endpoints using the libraries
2. Add the JavaScript Widget to your site
3. Verify submissions with the server libraries

Migration Guides

• Migrating from v2
• Migrating from reCAPTCHA
• Migrating from hCaptcha
• Migrating from Cloudflare Turnstile

Enterprises

If you’re looking for enterprise-specific documentation, visit the For Enterprises page.