How to Use Math Captcha in WordPress

What Is the Math Captcha feature?

The Math Captcha feature adds a simple math problem to your forms. Users see a question like “What is 3 + 5?” and must enter the correct answer. This is a self-contained captcha that doesn’t depend on Google, Cloudflare, or any third-party service.

Why You Need It

Traditional captchas have trade-offs:

• Image captchas: Bad for accessibility, can be bypassed by OCR
• Google reCAPTCHA: Tracks users across the web, requires Google account
• Cloudflare Turnstile: Requires Cloudflare account, can be rate-limited
• hCaptcha: Better than reCAPTCHA but still some tracking

Math captcha is different:

• No external service: Self-contained, no third-party API calls
• No tracking: Doesn’t follow users across the web
• Accessibility-friendly: Doesn’t require identifying objects in images
• Language-independent: Numbers are universal

For most basic spam protection, math captcha is sufficient.

How to Use Math Captcha in WordPress

Step 1: Navigate to Settings

Click into the Classic Monks plugin settings in your WordPress dashboard.

Step 2: Go to the Security Tab

Click on the Security menu, then click the WP Protection subtab.

Step 3: Enable Math Captcha

Scroll to Enable Math Captcha and toggle on. Nested options expand.

Step 4: Configure Form Scope

Select which forms get the math captcha:

• WordPress Login Forms: Login, registration, password reset
• WooCommerce Forms: Login, registration, checkout
• Comment Forms: Standard WordPress comments
• Frontend Post Submission: Frontend post submission plugins

Step 5: Save Changes

Click Save Changes.

Step 6: Test

Visit the login form (or whatever form you enabled). The math captcha should appear.

Configuration Options

Option	Description	Default
Enable Math Captcha	Master toggle.	Off
WordPress Login Forms	Apply to WP login forms.	On
WooCommerce Forms	Apply to WC forms.	On
Comment Forms	Apply to comments.	On
Frontend Post Submission	Apply to frontend submission forms.	On

The math problem is randomly generated for each form load. The numbers are between 1 and 10 by default.

What Gets Affected

• The login form: shows a math captcha
• The registration form: shows a math captcha
• The password reset form: shows a math captcha
• WooCommerce forms: shows a math captcha
• The comment form: shows a math captcha
• Form submission: requires the correct answer to succeed

What Does NOT Get Affected

• The admin (after login): not affected
• The form fields: only the captcha is added
• The user experience: math problems are quick (1-2 seconds)
• The form data: submitted normally once captcha passes

Advanced Options (Developers)

This feature registers 6 WordPress hooks in math-captcha.php:

Actions:

• login_form calls CM_Math_Captcha::render_captcha() (Renders captcha on login form)
• register_form calls CM_Math_Captcha::render_captcha() (Renders captcha on registration form)
• woocommerce_login_form calls CM_Math_Captcha::render_captcha() (Renders captcha on WooCommerce login)

Filters:

• authenticate calls CM_Math_Captcha::validate_login_captcha() (Validates captcha during login (priority 30))
• comment_form_field_comment calls CM_Math_Captcha::add_captcha_to_comment_form() (Adds captcha to comment form)
• preprocess_comment calls CM_Math_Captcha::validate_comment_captcha() (Validates captcha for comments)

// Hooked in math-captcha.php
add_action( 'login_form', 'CM_Math_Captcha::render_captcha' );

The feature modifies WordPress behavior by registering or removing hooks. Disabling it reverses those changes and WordPress returns to its default behavior.

Troubleshooting

Math captcha is not showing

Cause: The toggle is off, or the form scope doesn’t include the form you’re testing.
Fix: Verify the toggle is on. Verify the form scope includes the form (e.g., WP Login Forms for the login form).

Math captcha is showing but the form rejects correct answers

Cause: A JavaScript error or theme conflict is preventing the form from submitting.
Fix: Check the browser console for errors. Disable other form-related plugins to find the conflict. Test with a default theme.

The math problem is too easy

Cause: The default range is 1-10 with addition only.
Fix: The captcha uses simple addition and subtraction by default. If you need harder questions, consider using the Cloudflare Turnstile feature instead.

The math problem is too hard for some users

Cause: The math may be challenging for users with cognitive disabilities or non-native speakers.
Fix: Use a smaller number range. Consider adding an audio captcha option. Some sites provide both math and image captcha options.

The captcha is bypassed by automated bots

Cause: Sophisticated bots can solve math captchas.
Fix: For high-value forms (login, registration), use Cloudflare Turnstile instead. For low-value forms (comments), math captcha is usually sufficient. Consider adding Login Lockdown to complement.