Free, open-source
Captcha alternative
Unlike other solutions, ALTCHA is free, open-source and self-hosted, does not use cookies nor fingerprinting, does not track users, and is compliant with data-privacy regulations and accessible.
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.
More than just
a Captcha protection
ALTCHA represents a modern, accessible, and inclusive approach to safeguarding websites, APIs, and online services from spam and abuse.
Its fundamentally different approach makes it ideal for businesses constrained by privacy regulations in the EU and around the world.
Compliant with Regulations
Comply with GDPR/HIPAA/CCPA/LGPD/DPDPA/PIPL by using a privacy-first solution that does not use cookies nor fingerprinting and does not track users. Learn more.
Complete Spam Protection
Utilize the proof-of-work mechanism as the initial line of defense. Then, stop even sophisticated attacks and human-generated spam with ALTCHA Sentinel.
Friendly to Humans
Say goodbye to tedious puzzle-solving and improve your website's UX by integrating a fully automated proof-or-work mechanism. Try demo.
Inclusive to Robots
Get ready for AIs and integrate M2M ALTCHA into your APIs and online services making them accessible to machines. See how.
Open source, MIT licensed
ALTCHA is a free, open-source project licensed under a permissive MIT license. Works for everyone - individuals, small businesses and enterprises. Visit GitHub.
Try Captcha verification for humans
ALTCHA’s web component is familiar to users and easy to integrate into any website.
Check the box to get verified.
Try Machine-to-Machine (M2M) ALTCHA
M2M ALTCHA works as a rate-limiter implemented on the consumer’s end. It helps you protect expensive resources, reduce spam and abuse in your online services and APIs while keeping them accessible to automated systems.
Read more about M2M ALTCHA →
For integration, follow the documentation.
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.
ALTCHA Sentinel vs Open Source
| ALTCHA Sentinel | Open Source | |
|---|---|---|
| Data Privacy Compliant with data-privacy regulations. | | |
| Accessibility Fully accessible interface following WCAG guidelines. | | |
| Self-hosted Fully self-hosted on your own infrastructure without external services. | | |
| Ready-to-use All-in-one Docker image with easy deployment options. | | |
| Adaptive Captcha Frictionless experience with extra verification for flagged users. | | |
| Text Classifier Built-in text classifier powered by machine learning. | | |
| Training Data Uses machine learning datasets to improve spam detection. | | |
| Language Detection Identifies and filters content based on detected languages. | | |
| Bot Detection Detect and block bots, crawlers, and AI agents. | | |
| IP Reputation Resolve IP addresses and detect proxies, TOR networks and malicious actors. | | |
| IP Geo Fencing Restrict or allow access based on geographic location. | | |
| Email Verification Verify email addresses and prevent fake sign-ups. | | |
| Rate Limiter Protect against brute force attacks with request rate limiting. | | |
| Form Submissions Built-in form capture API with spam filtering. | | |
Explore the features and documentation of ALTCHA Sentinel for more information.
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!