GDPR Compliant
Captcha and Bot Protection
Secure your data and users with the privacy-first alternative to reCAPTCHA. ALTCHA eliminates tracking, cookies, and fingerprinting, delivering a robust, accessible, and globally compliant security without a single puzzle.
100% self-hosted • No external calls • No data sharing.
Captcha with Global Compliance and Universal Accessibility
Adaptive Bot Protection
ALTCHA Sentinel delivers automated, adaptive bot protection that dynamically responds to emerging threats.
Code Captcha
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 of Captcha 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 Captcha experience in 50+ languages for everyone.
Bundle Size
Smaller bundle size means faster load times.
Assets are gzipped and minified.
ALTCHA with all 50+ languages included totals 46 kB.
Load Time
Faster load time means a better user experience.
How does ALTCHA load instantly? By bundling the ALTCHA widget directly into your website’s code using tools like Vite or Webpack.
ALTCHA is available as a JavaScript npm package.
The Sentinel Advantage
Security, compliance, and performance — all in one solution.
Secure
Block bots, spam, and malicious traffic before it reaches your systems. Sentinel keeps your websites, apps, and services safe with on-premise protection you fully control.
Comply
Meet data protection and privacy requirements with a solution that never leaks sensitive information to third parties. Stay aligned with GDPR and enterprise compliance standards.
Optimize
Reduce noise, improve performance, and focus on real users. With spam filtered at the source, your analytics, workflows, and support channels stay accurate and efficient.
Multi-Layered Protection
ALTCHA Sentinel applies multi-layered detection to stop bots in real time.
Distinguishes real users from bots using an accessible, frictionless captcha that adapts to each interaction.
Analyzes IP addresses against databases of known abusers, detects phishing URLs, and dynamically learns from your own user activity.
Inspects the user's device for automation markers and suspicious configurations commonly associated with bots and scripted attacks.
Detects harmful content, spam, and phishing links in submitted data — allowing only legitimate and safe input through.
Controls the frequency of interactions using configurable thresholds to prevent abuse, brute-force attempts, and DDoS attacks.
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 bots 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.
Automatically detects and blocks malicious IPs and phishing URLs.
Restricts access based on geographic location of IP addresses.
Identifies and filters content based on detected languages.
Secures form submissions against bots and automated attacks.
Protect any URL with a verification page before redirecting users to the destination.
Trusted by Institutions and Businesses Worldwide
Enterprise & Government Solutions
ALTCHA provides enterprise-grade anti-bot 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.
Easy Captcha integration
ALTCHA Sentinel is a self-hosted solution with straightforward integration. A 30-day trial begins automatically upon installation.
Examples
See example setups of ALTCHA with different front-end frameworks:
Widgets
Add the ALTCHA widget to your website or app:
Server Libraries
On your backend (server), verify the ALTCHA payload to validate user interactions and form submissions:
Plugins
Visit the Integrations documentation for more community-developed libraries and plugins.
Robust Captcha Alternative
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.
Spam Protection Without Compromising Privacy And Accessibility
ALTCHA - The accessible, privacy-first reCAPTCHA alternative
| ALTCHA | reCAPTCHA | |
|---|---|---|
| Privacy friendly Captcha Fully GDPR/HIPAA/CCPA/LGPD/DPDPA/PIPL compliant - No cookies, no tracking, no external servers | ||
| Accessible Captcha WCAG/EAA compliant - Captcha 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 Captcha 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.
Self-Hosting Sentinel
Sentinel provides a powerful spam protection platform with simple Docker-based deployment. Get started with Sentinel.
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