OpenPorte Spam Protection for WordPress Plugin Directory

OpenPorte is a free and open-source plugin that protects WordPress forms

from spam using a lightweight Proof-of-Work challenge instead of CAPTCHAs.

The goal is to make spam expensive for bots while keeping the experience almost

invisible for legitimate visitors and respecting their privacy.

For site owners, OpenPorte offers an easy to configure and deploy modern

spam protection under their control.

For the site users, it offers an accessible, transparent and privacy-friendly

alternative to CAPTCHAs.

OpenPorte is built around the open-source ALTCHA widget.

Some highlights:

CAPTCHA-free spam protection

Fully open source (GPL)

Self-hosted – no mandatory external service

Designed to be accessible and privacy-friendly

Compatible with existing ALTCHA integrations

Easy migration for users of ALTCHA Spam Protection v1 (≤ 1.26.3)

For the list of contributors, refer to our GitHub project: Contributors.

AI-assisted development AI-assisted project. Architecture, security decisions, and final review are

mine; AI tools (Claude, Mistral, and others) help with drafting code, tests,

translations, and documentation — without them, one person couldn’t keep

this fork alive.

Background The original ALTCHA Spam Protection WordPress plugin (v1) was open source

(GPLv2). Its authors have since released a version 2/3 which is no longer

open source. They no longer maintain the open source project and recommend

that users migrate to v2/v3. See the official project at https://altcha.org

for their offering.

OpenPorte started as a fork and continues the v1 line as free software

(GPLv2 or later) for users who want to stay on a fully open-source,

self-hosted solution. It is a faithful fork: existing v1 installations

can switch to OpenPorte and keep their settings (see Upgrading).

Compatibility OpenPorte is backward-compatible with ALTCHA Spam Protection v1 plugin:

Your existing settings are migrated automatically on activation.

The [altcha] shortcode keeps working (alongside the new [openporte]).

The altcha_* filters and actions keep firing as deprecated aliases.

Custom API Mode has been verified against GateCHA,

an open source server implementing the creation and verification of ALTCHA challenges.

See the Deprecations section for the full list of compatibility aliases and

what they map to.

Upgrading From the original ALTCHA v1 plugin Deactivate the old ALTCHA plugin, then install and activate OpenPorte. Your

existing configuration is detected and copied into the OpenPorte settings on

first activation; the original ALTCHA settings are left untouched, so you can

roll back to ALTCHA v1 without losing anything. Do not run both plugins at the

same time.

From ALTCHA v2/v3 If your site was already moved to ALTCHA v2/v3 (for example by the automatic

3.0.0 update), your original v1 settings are normally still in the database:

the v2/v3 upgrade neither migrates nor removes them. Deactivate ALTCHA, then

install and activate OpenPorte — it finds and imports the v1 settings, even

when the v1 plugin itself has long been deleted. Settings made in v2/v3 are

not read.

Deprecations The following ALTCHA-era identifiers are kept as aliases for backward

compatibility and are scheduled for removal in a future release:

The [altcha] shortcode — use [openporte].

The altcha/v1 REST namespace — use openporte/v1.

The altcha_* filters and actions — now firing through WordPress’ deprecated

hook mechanism; use the openporte_* equivalents.

The AltchaPlugin class and the ALTCHA_VERSION / ALTCHA_WIDGET_VERSION

constants — use OpenPortePlugin and the OPENPORTE_* constants.

Integrations targeting paid-only third-party plugins; affected users should

migrate to the official ALTCHA v2/v3 plugin.

The “Custom HTML” integration (auto-configuration of hand-written

tags) — place the [openporte] shortcode instead. You can

re-enable it for now under Settings → OpenPorte → Integrations.

Privacy No cookies, no tracking OpenPorte prioritizes user privacy by avoiding the use of cookies and fingerprinting techniques.

No external service This plugin remains fully contained within your WordPress installation, eliminating any reliance on external services.

Modes of Operation OpenPorte verifies submissions in one of two modes, selected in the settings

(API Mode):

Self-hosted (default) — a proof-of-work challenge is issued and verified by

your own WordPress site through the REST API. Fully self-contained, with no

external service and no additional setup beyond enabling the integrations you

need.

Custom — point the Challenge URL at your own ALTCHA-compatible backend (for

example a self-hosted ALTCHA Sentinel, or GateCHA).

Submissions are verified with your site’s shared secret.

The paid altcha.org regional SaaS classifier offered by earlier versions has

been removed; both remaining modes are free and self-hostable.

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 (marked for deprecation) and /openporte/v1/challenge are allowed.

Supported Integrations

CoBlocks

Contact Form 7

Elementor Pro Forms (deprecated — paid plugin, see Deprecations)

Formidable Forms

Forminator

GravityForms

HTML Forms

wpDiscuz

WPForms

WordPress Login, Register, Password reset

WordPress Comments

WooCommerce

Many other plugins and your own content (via the [openporte] shortcode, or the deprecated [altcha] alias)

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/openporte/openporte

ALTCHA Widget: https://github.com/altcha-org/altcha