ExpressionEngine Docs

# CAPTCHAs

- Comment Forms
- Member Registration Form
- Contact and Tell-a-Friend Email Forms
- CAPTCHA Code
- Notes
- CAPTCHA Words

ExpressionEngine supports what are known as “CAPTCHAs”, or Completely Automated Public Turing tests to tell Computers and Humans Apart. A CAPTCHA is a computer-generated test that humans can easily pass, but that is computationally difficult for a computer to do.

So how does this work? An image is generated in real time for a user loading a web page. This image contains a word that the user must enter in a form. The concept is effective because computers are generally not very good at reading images, but it is something humans can do with little effort.

In ExpressionEngine, CAPTCHAs can be used in several places:

- CAPTCHAs - Comment Forms - Member Registration Form - Contact and Tell-a-Friend Email Forms - CAPTCHA Code - Notes - CAPTCHA Words

The settings to require CAPTCHAs for these forms are located at `Settings --> CAPTCHA` in the control panel.

## Comment Forms

Once you have the preference turned on, you’ll need to add the CAPTCHA code to your Comment Submission Form. See below for the CAPTCHA Code.

## Member Registration Form

The necessary CAPTCHA code already exists in the Member Templates by default, so you should not need to add it. If you have a version of ExpressionEngine from before the CAPTCHA feature was added or if you otherwise need the code, see below for the CAPTCHA Code.

## Contact and Tell-a-Friend Email Forms

Once you have the preference turned on, you’ll need to add the CAPTCHA code. See below for the CAPTCHA Code.

## CAPTCHA Code

    {if captcha}
        <p>Please enter the word you see in the image below:</p>
        <p>{captcha}<br /> <input type="text" name="captcha" value="{captcha_word}" size="20" maxlength="20" style="width:140px;" /></p>
    {/if}

The contents of the conditional {if captcha} tag will only appear if you have the CAPTCHA preference turned on for either the comment or member registration forms.

The code used inside the Member Registration Form is very similar, with only the omission of the {captcha_word} variable:

    {if captcha}
        <p>Please enter the word you see in the image below:</p>
        <p>{captcha}<br />
        <input type="text" name="captcha" value="" size="20" maxlength="20" style="width:140px;" /></p>
    {/if}

## Notes

It is important to note that there is a downside to using CAPTCHAs. While they can be very successful in stopping automated bots from being able to post comments or sign up for memberships, it can also have the same effect on blind or visually impaired users of your site. If you enable CAPTCHAs, then you will be making it extremely difficult for these legitimate users to be able to use your site.

You should determine for yourself whether or not CAPTCHAs are appropriate for your situation and your website audience.

For ExpressionEngine installations that power multiple domains or subdomains, you may need to place the server path for the Relative Path to Captcha Folder setting under `Settings --> CAPTCHA`. A server path is typically something similar to /home/domain.com/http_docs/images/captchas/. The specific setting will vary from server to server so you may need to contact your Host or server admin to determine what your correct “server path” is.

## CAPTCHA Words

The CAPTCHA system uses a default dictionary. You can override these by adding a special user config file and returning an array of words you want to use instead. Create a PHP file at `system/user/config/captcha.php` with the format:

    <?php

    return [
      'your',
      'words',
      'here',
      /* ... */
    ];