Description

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

Screenshots

Friction-less Captcha without puzzles
Configuration
Protection on the login page
Protection with WPForms
Floating UI Captcha

Installation

Download, install and activate ALTCHA Spam Protection.

Alternatively, install the plugin manually:

Download the .zip from the Releases.
Upload altcha folder to the /wp-content/plugins/ directory
Activate the plugin through the ‘Plugins’ menu in WordPress
Review the settings and enable your integrations

Reviews

Hiroshi November 24, 2025

its a simple plugin easy to setup and work well with my websites… so far eliminated almost all spam +1

abaantravis November 22, 2025

I personally find this plugin very useful and working just fine, no problems. I don’t understand why people here complain. Great work, thanks! And please keep this plugin alive.

sarahsolus November 17, 2025

The version 1 Altcha WordPress plugin was a promising, if not perfect, captcha plugin. Unfortunately, the developers got everything wrong with version 2. First of all, it can only be installed via the website, which is suspicious. There are no upgrade notes, which is an absolute no-go for commercial sites. Incidentally, a captcha that installs itself into all forms without being asked is a very bad idea. For example, Altcha v2 also activates when using form-like elements such as filter widgets for lists. Or in globally integrated service forms, so that the Altcha screen pops up on every page. We also suspect that Altcha v2 prevents AI search engines from crawling – this has not yet been verified, but it coincides with the use of the plugin. For all these reasons, we have decided to stop using the plugin for the time being.

Alwyn Barry November 17, 2025

Altcha v1 was brilliant – did just what I wanted seamlessly. Sadly when I installed v2 the login blocked for some users (and it was impossible to see why). I think the increased comms to the central system were to blame, but I’m not sure. I can’t switch back to v1 without having the ‘nag’ to upgrade constantly visible on the plugin page, and putting the shortcode back into all the forms. A quick switch to Cloudfare Turnstile and all is working nicely. Sad, though, because Altcha looked great.

riccardomercurio November 7, 2025

It is simple it works!

agent862 November 7, 2025

It’s free, works without any API or cloud services, no cookies, which all means GDPR and other privacy regulations are in check. 👍

Read all 21 reviews

Contributors & Developers

“ALTCHA Spam Protection” is open source software. The following people have contributed to this plugin.

Daniel

“ALTCHA Spam Protection” has been translated into 2 locales. Thank you to the translators for their contributions.

Translate “ALTCHA Spam Protection” into your language.

Interested in development?

Browse the code, check out the SVN repository, or subscribe to the development log by RSS.

Changelog

1.26.2

Updated readme for the new version 2.

1.26.1

Fix Elementor Pro Forms widget rendering

1.26.0

Added Formidable Forms integration
Fixed PHP warning in the verify function
ALTCHA Widget 2.2.2

1.25.0

Added hooks for improved customization and integration flexibility. [#45]

1.24.0

Fix issue with duplicate widget rendering in Elementor popups and WPDiscuz replies

1.23.0

Support for CoBlocks

1.22.1

Fix Gravity Forms validation with custom server

1.22.0

Fix Forminator multi-page forms
Fix Gravity Forms with Sentinel and fields classification

1.21.0

ALTCHA Widget 2.0.2
Widget scripts are now injected only on pages, which include the widget
Support for custom Challenge URL and ALTCHA Sentinel

1.20.0

Enfold Theme (contact and newsletter forms) integration

1.19.0

Fix submit issues with Contact Form 7 + Conditional fields

1.18.0

Fix language with Contact Form 7

1.17.0

Update widget to 1.2.0
Widget removes support for Expires header fixing potential auto-revalidation issues
Widget script provided as a UMD module allowing for JS minification

1.16.0

Fix reply to comments from the admin page [#36]

1.15.0

Translations with gettext and automatic language detection [#33]

1.14.1

Fix the “Settings” link [#32]

1.14.0

Automatic language detection [#31]
Change placement of the “Settings” link in the plugin list [#32]

1.13.1

Ignore WooCommerce form submissions in WordPress integration [#30]

1.13.0

WooCommerce integration [#26]
Improved validation message [#27]
Password lost error message [#28]

1.12.0

HTML Forms – skip verification if the shortcode is not in the form markup [#23]

1.11.1

Fix Forminator compatibility issue

1.11.0

Added support for WP-Members

1.10.0

Added support for WPDiscuz

1.9.3

Fix REST API Cache-Control header

1.9.2

Enable Custom HTML (shortcode) integration by default when activated

1.9.1

PHP 7 support (replace str_contains by strpos) [#19]

1.9.0

Widget updated to version 1.0.0
CF7 – fix widget placement
Fix page caching

1.8.0

Shortcode (custom integration) – fix mode (SpamFilter)

1.7.0

HTML Forms – add Shortcode option

1.6.1

Fix WordPress login integration

1.6.0

Fix Elementor Pro Forms widget rendering
Fix Contact Form 7 widget position and shortcode support

1.5.0

Fix REST base URL (+ REST prefix removed from settings) [#13]

1.4.0

Support for Elementor Pro Forms
Widget updated to 0.6.7

1.3.1

Fix site_url parsing issue [#11]

1.3.0

Added support for custom REST API prefixes

1.2.0

Forminator – fix widget rendering with file input
Widget updated to 0.6.4

1.1.0

Shortcode – support for language attribute

1.0.0

Widget updated to 0.6.3

0.3.0

Added nonce sanitization
Removed server-side spam filter (required for Plugin Directory)

0.2.1

Fixes requested by Plugin Directory review
Fixed various Spam Filter issues

0.2.0

Widget updated to 0.6.0
Added support for Floating UI

0.1.7

Fix Forminator multi-step forms

0.1.6

Widget updated to 0.5.1

0.1.5

Fixes requested by Plugin Directory review

0.1.4

GravityForms – added label and description options
Altcha widget updated to 0.4.3

0.1.3

Fixed “lost password” verification bug
Altcha widget updated to 0.4.1

0.1.2

Fixed widgets footer link and log warnings

0.1.1

Widget v0.4.0
Challenge expiration

0.1.0

First version