Next-Gen Captcha
and Spam Protection
ALTCHA Sentinel is a next-generation security system that stops bots and automated threats — without frustrating real users. It intelligently adapts to risks, blending advanced detection with seamless verification to keep your apps and services protected.
Sentinel works quietly in the background, using machine learning and pattern recognition to block abuse. Whether you’re defending sign-ups, forms, or APIs, it delivers robust security while maintaining a smooth and accessible experience for legitimate traffic.
ALTCHA is a self-hosted solution that ensures compliance with data protection and accessibility regulations worldwide.
Compliant with the General Data Protection Regulation.
Compliant with the Health Insurance Portability and Accountability Act.
Compliant with the California Consumer Privacy Act.
Compliant with the Canadian Consumer Privacy Protection Act.
Compliant with the Brazilian General Data Protection Law.
Compliant with India’s Digital Personal Data Protection Act.
Compliant with the Personal Information Protection Law of the People’s Republic of China.
ALTCHA Sentinel delivers automated, adaptive spam protection that dynamically responds to emerging threats.
Frictionless Verification
The system defaults to a Proof-of-Work (PoW) verification method, eliminating visual puzzles or disruptive challenges. This approach balances security with accessibility, offering an unobtrusive solution suitable for most users.
Code Challenge
For cases flagged as high-risk, the protection escalates to a secure code challenge. This includes an audio component, ensuring adherence to accessibility regulations like EAA and WCAG without compromising security.
* This is a demonstration showing only the user interface without full functionality.
ALTCHA speaks your language — literally. With multilingual audio code-challenges, automatic translations, and RTL support, ALTCHA delivers a seamless experience in 48+ languages for everyone.
Self-hosted, machine learning-powered defense against spam, bots, and automated attacks.
Block fake sign-ups and bot-created accounts with challenge-based verification.
Defend against credential stuffing and brute-force attacks on logins.
Stop spam in contact forms, surveys, and submissions without hurting user experience.
Filter spam in discussions and forums, reducing moderation work.
Block malicious bot traffic across web services and APIs to stop data scraping, service overload, and unauthorized access.
Keep spam and phishing attempts out of your email ingress.
ALTCHA Sentinel is packed with security features that help you protect your apps and services.
Adjusts difficulty based on user behavior to block bots effectively.
Analyzes and categorizes text inputs for malicious content.
Uses machine learning datasets to improve spam detection.
Identifies and blocks automated bots, crawlers and AI agents.
Flags requests from proxy servers or TOR networks.
Validates email addresses to reduce fake sign-ups.
Prevents abuse by limiting requests from a single source.
Checks IPs against known threat databases.
Restricts access based on geographic location of IP addresses.
Identifies and filters content based on detected languages.
Secures form submissions against spam and automated attacks.
Integrate Sentinel into your APIs and backend services.
ALTCHA provides enterprise-grade anti-spam protection for businesses and government organizations that require stringent compliance with global regulations, including data protection standards and the European Accessibility Act (EAA). Designed for security-conscious enterprises, ALTCHA ensures robust spam prevention while meeting the highest standards of privacy and accessibility.
ALTCHA Sentinel is a self-hosted solution with straightforward integration. A 30-day trial begins automatically upon installation.
Migration guides:
Examples
See example setups of ALTCHA with different front-end frameworks:
Official Libraries
ALTCHA’s TypeScript library runs everywhere! Whether it’s modern browsers, Node.js, Bun, Deno, or any WinterCG-compatible runtime.
Plugins
Visit the Integrations documentation for more community-developed libraries and plugins.
Robust Spam Protection and Privacy
ALTCHA offers a powerful, self-hosted alternative to traditional CAPTCHAs, putting privacy and transparency first. As an open-source solution, it gives you full control over your spam protection system, eliminating reliance on third-party services that may track user data.
Unlike other options, ALTCHA is fully customizable, allowing you to tailor the challenge mechanism to your specific needs while ensuring GDPR compliance. Its lightweight design ensures fast, frictionless verification for real users while effectively blocking bots—all without compromising user privacy.
Stop Spam Without Compromising Privacy
ALTCHA - The accessible, privacy-first alternative to reCAPTCHA
| ALTCHA | reCAPTCHA | |
|---|---|---|
| Privacy Fully GDPR/HIPAA/CCPA/LGPD/DPDPA/PIPL compliant - No cookies, no tracking, no external servers | | |
| Accessibility WCAG/EAA compliant - Works with screen readers and assistive tech | | |
| User Experience Frustration-free - No visual puzzles - Self-verifying proof-of-work | | |
| Customization Fully adjustable security - Customize widget behavior and appearance | | |
| Advanced Security Comprehensive protection - ALTCHA Sentinel for advanced security | | |
| Open Source Core Core available as open-source (MIT) - Free to use and modify with optional commercial ALTCHA Sentinel | | |
The open-source widget and integration libraries provide free integration of ALTCHA for websites, apps, and services. While the open-source version’s proof-of-work mechanism offers basic protection, ALTCHA Sentinel delivers enhanced security for mission-critical deployments.
Get Started
with ALTCHA
Sentinel provides a powerful spam protection platform with simple Docker-based deployment. Get started with Sentinel.
Explore our free, open-source CAPTCHA alternative. Learn how to integrate it.
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