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Try ALTCHA Sentinel for comprehensive, self-hosted spam protection.
Captcha with GDPR compliance Captcha with GDPR compliance

Next-Gen Captcha
and Spam Protection

ALTCHA provides privacy-first spam protection with a globally compliant and accessible alternative to CAPTCHAs. Protects against spam and abuse without tracking users, complying with GDPR, CCPA, and other regulations while ensuring a frictionless experience.

ALTCHA Sentinel

Self-hosted spam protection for websites, apps, and services.

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.

AWS

Azure

Kubernetes

Docker

ALTCHA Sentinel - Spam and Abuse Protection
Global Compliance, Universal Accessibility

ALTCHA is a self-hosted solution that ensures compliance with data protection and accessibility regulations worldwide.

EU

USA

Canada

Australia

Brazil

India

China

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.

Adhering to the WCAG 2.2 guidelines for AA-level compliance.

EAA

Fully compliant with WCAG 2.2 Level AA, meeting all accessibility requirements under the European Accessibility Act (EAA).

Internationalization with support for over 48 languages, including RTL (right-to-left) support.

Adaptive Protection

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.

Understandable and Inclusive

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.

Use Cases

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.

Beyond Captchas

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.

Trusted by Institutions and Businesses Worldwide
gouv.fr
gov.uk
usp.gv.at
University of London
Enterprise & Government Solutions

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.

Learn more

Easy integration

ALTCHA Sentinel is a self-hosted solution with straightforward integration. A 30-day trial begins automatically upon installation.

  1. Install on your infrastructure
  2. Add the widget to your site

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.

ALTCHA vs Captcha Comparison

ALTCHA vs Captcha Comparison - Protection and Privacy Compliance

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

Open Source vs 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

Self-Hosting Sentinel

Sentinel provides a powerful spam protection platform with simple Docker-based deployment. Get started with Sentinel.

Open Source Core

Explore our free, open-source CAPTCHA alternative. Learn how to integrate it.

Copyright © 2024 Altcha.org - Dedicated to Privacy.

ALTCHA ® is a trademark registered in EU.

Project sponsored by BAUSW.com - Digital Construction Site Diary, promoting transparency and trust in construction projects with real-time documentation.

OSS hosted on GitHub • Website made with Astro Starlight.

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Support us by giving us a star on GitHub!

ALTCHA is made in Europe.
Element 1
Hosted by Hetzner, Germany.
CDN by bunny.net, Slovenia.
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