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Introducing ALTCHA Forms + Paid plans for the API and the Spam Filter.
GDPR compliant Captcha GDPR compliant Captcha

Free, open-source
Captcha alternative

ALTCHA uses a proof-of-work mechanism to protect your website, APIs, and online services from spam and unwanted content.

Unlike other solutions, ALTCHA is free, open-source and self-hosted, without external services, does not use cookies nor fingerprinting, does not track users, and is fully compliant with GDPR.
ALTCHA is a community-driven, open-source project.
Latest News
  • Explore the new Floating UI allowing for even smoother UX.
  • Introducing ALTCHA Forms - a secure data collection platform compliant with GDPR and HIPAA.
  • Paid plans for the API and the Spam Filter are now available.

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.

GDPR Compliant

Comply with GDPR 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 the Spam Filter.

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

Is it a good Captcha alternative for you?

Read more about ALTCHA’s effectiveness

Are you a human?

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.

Protected form

This is just a demo. Your message won't be submitted anywhere.

Eliminating Spam

Smart Spam Filter

ALTCHA’s GDPR-compliant Spam Filter provides an additional protective layer by analyzing incoming data through natural language processing and machine learning, distinguishing between legitimate data and spam.

Now available for integration on your website. For Free!

Safeguarding Data



ALTCHA Forms enables secure data collection through registration and personal data forms, questionnaires, and surveys, ensuring compliance with data protection regulations such as GDPR or HIPAA.

Are you a robot?

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

Easy integration

ALTCHA API is a SaaS platform allowing you to integrate quickly. It’s available for free to anyone without registration.

  1. Create a free API Key
  2. Add the widget to your website:
<!-- Add <script> tag -->
<script async defer src="" type="module"></script>
<!-- Use <altcha-widget> tag in your forms -->
<altcha-widget challengeurl=""></altcha-widget>

Refer to the documentation for more details about integration.


Visit the Integrations documentation for more community-developed libraries and plugins.

A privacy-friendly solution to spam control

ALTCHA is an open-source alternative to reCAPTCHA and similar solutions

Privacy-friendly, GDPR compliant

No cookies, no tracking, no external servers.


No visual puzzles. PoW Captcha is better for people.


Works automatically, without requiring user interaction.


Adjust the complexity of the PoW and widget branding to your needs.


All humans and all robots are welcome. M2M ALTCHA can be implemented on any system.

Spam Filtering

Employs machine learning to categorize submitted data and identify unwanted messages.


Free to use, free to modify. MIT licensed.

ALTCHA is a free open-source project hosted on GitHub. MIT licensed. Feel free to contribute.

Developed as a privacy-respecting alternative to Captcha and other popular solutions, ALTCHA is a better way to shield your website and online services from spam and abuse while protecting your user’s privacy.

Copyright © 2024 - Dedicated to Privacy.

OSS hosted on GitHub • Website made with Astro Starlight.

Crafted in EU, with Europeans in mind.
Hosted in Germany. USA region available.

Do you like ALTCHA?
Support us by giving us a star on GitHub!