Really Simple CAPTCHA

Description

Really Simple CAPTCHA does not work alone and is intended to work with other plugins. It is originally created for Contact Form 7, however, you can use it with your own plugin.

Note: This product is “really simple” as its name suggests, i.e., it is not strongly secure. If you need perfect security, you should try other solutions.

How does it work?

Really Simple CAPTCHA does not use PHP “Sessions” for storing states, unlike many other PHP CAPTCHA solutions, but stores them as temporary files. This allows you to embed it into WordPress without worrying about conflicts.

When you generate a CAPTCHA, Really Simple CAPTCHA creates two files for it; one is an image file of CAPTCHA, and the other is a text file which stores the correct answer to the CAPTCHA.

The two files have the same (random) prefix in their file names, for example, “a7hk3ux8p.png” and “a7hk3ux8p.txt.” In this case, for example, when the respondent answers “K5GF” as an answer to the “a7hk3ux8p.png” image, then Really Simple CAPTCHA calculates hash of “K5GF” and tests it against the hash stored in the “a7hk3ux8p.txt” file. If the two match, the answer is confirmed as correct.

How to use with your plugin

Note: Below are instructions for plugin developers.

First, create an instance of ReallySimpleCaptcha class:

$captcha_instance = new ReallySimpleCaptcha();

You can change the instance variables as you wish.

// Change the background color of CAPTCHA image to black
$captcha_instance->bg = array( 0, 0, 0 );

See really-simple-captcha.php if you are interested in other variables.

Generate a random word for CAPTCHA.

$word = $captcha_instance->generate_random_word();

Generate an image file and a corresponding text file in the temporary directory.

$prefix = wp_rand();
$captcha_instance->generate_image( $prefix, $word );

Then, show the image and get an answer from respondent.

Check the correctness of the answer.

$correct = $captcha_instance->check( $prefix, $the_answer_from_respondent );

If the $correct is true, go ahead. Otherwise, block the respondent — as it would appear not to be human.

And last, remove the temporary image and text files, as they are no longer in use.

$captcha_instance->remove( $prefix );

That’s all.

If you wish to see a live sample of this, you can try Contact Form 7.

Screenshots

  • screenshot-1.png

Installation

In most cases you can install automatically from WordPress.

However, if you install this manually, follow these steps:

  1. Upload the entire really-simple-captcha folder to the /wp-content/plugins/ directory.
  2. Activate the plugin through the ‘Plugins’ menu in WordPress.

FYI: There is no “control panel” for this plugin.

FAQ

CAPTCHA does not work; the image does not show up.

Really Simple CAPTCHA needs GD and FreeType library installed on your server. Ask your server administrator if they are installed.

Also, make the temporary file folder writable. The location of the temporary file folder is managed by the instance variable tmp_dir of ReallySimpleCaptcha class. Note that the setting varies depending on the calling plugin. For example, Contact Form 7 uses wp-contents/uploads/wpcf7_captcha as the temporary folder basically, but it can use different folder depending on your settings.

If you have any further questions, please submit them to the support forum.

Reviews

August 19, 2024
Nothing but positives. We added this to our Gravity Form in order to obtain the dynamic math captcha. One can create a simple math captcha in GF but not dynamically changing for each form load insofar as I can determine. And GF google captcha Ver 3 is a pain with the need for google api keys. So we added this plugin and it was very easy – add the captcha field to the form, select “math” in the settings for the field and done! We find that Gravity Forms Zero Spam plugin was helping to deter spam entries but it with this captcha is 100% so far for spam prevention. Thank you Takayuki Miyoshi!
October 25, 2023
Helo, very simple banner for cookies but there is a little bug. The banner Cookies are shown in Widgets page.
December 17, 2021
Needed this for an installation with custom forms. I used the plugin developers instructions and was able to make a fully custom implementation based on server side validation within 30 minutes. No more spam bots misusing the forms. Thank you!
Read all 126 reviews

Contributors & Developers

“Really Simple CAPTCHA” is open source software. The following people have contributed to this plugin.

Contributors

“Really Simple CAPTCHA” has been translated into 41 locales. Thank you to the translators for their contributions.

Translate “Really Simple CAPTCHA” into your language.

Interested in development?

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

Changelog

2.3

  • Bumps up the minimum required WordPress version to 6.4.

2.2

  • Bumps up the minimum required WordPress version to 6.1.
  • Bumps up the minimum required PHP version to 7.4.
  • Replaces ReallySimpleCaptcha::normalize_path() with wp_normalize_path().
  • Updates Apache directives.