ALTCHA Spam Protection

This is ALTCHA Plugin version 1.

ALTCHA Plugin version 2 is now available, offering improved protection and enhanced reliability. An upgrade is recommended for all users.

Learn more | Installation guide | Migration guide

What’s new in version 2:

• Effective: blocks 99% of spam and abuse attempts
• Invisible for users: frictionless protection, no puzzles or CAPTCHAs
• Works everywhere: plugin-agnostic Request Interceptor integrates with any form plugin
• Handles heavy traffic: stay online with Under Attack Mode
• Stops abuse at scale: firewall and rate limiting included
• Privacy-first: 100% GDPR-compliant and fully accessible
• Unlimited: no external services, unlimited verifications

Learn more about ALTCHA at altcha.org.

ALTCHA provides a free, open-source Captcha alternative utilizing a proof-of-work mechanism to safeguard your website against spam and unwanted content. Our anti-spam solution ensures robust spam protection without compromising user privacy.

Unlike other solutions, ALTCHA is free, open-source, and self-hosted. It operates independently without external services, avoids the use of cookies and fingerprinting, refrains from user tracking, and maintains full compliance with GDPR regulations.

Free Mode

The free self-hosted mode is enabled by default after installation. No additional setup is required, except enabling the integrations you need in the plugin settings.

Privacy

No cookies, no tracking

ALTCHA prioritizes user privacy by avoiding the use of cookies and fingerprinting techniques.

No external service

Operating in Self-hosted mode (the default setting), this plugin remains fully contained within your WordPress installation, eliminating any reliance on external services. You can opt-in for our SaaS version to utilize the Spam Filter API. For more information visit https://altcha.org.

Modes of Operation

This plugin operates in two modes, you can select which mode you want in the settings (see API Region):

• Self-hosted – free, fully self-contained without external services.
• Custom or SaaS API – requires a server such as ALTCHA Sentinel.

REST API

This plugin requires the WordPress REST API. If you are using any “Disable REST API” plugins, ensure that the endpoint /altcha/v1/challenge is allowed.

Supported Integrations

• CoBlocks
• Contact Form 7
• Elementor Pro Forms
• Enfold Theme
• Formidable Forms
• Forminator
• GravityForms
• HTML Forms
• WPDiscuz
• WPForms
• WP-Members
• WordPress Login, Register, Password reset
• WordPress Comments
• WooCommerce
• Custom HTML (with a short code [altcha])

Source Code

All source code for the plugin, and the ALTCHA widget is available on GitHub. In the repository, you’ll also find versions of non-minified JavaScript and CSS assets:

• Plugin: https://github.com/altcha-org/wordpress-plugin
• ALTCHA Widget: https://github.com/altcha-org/altcha

Terms of Service And Privacy Policy for SaaS

• Privacy Policy: https://altcha.org/privacy-policy
• Terms of Service: https://altcha.org/terms-of-service