CAPTCHA Requirements

Checking CAPTCHA requirements

The most common requirement of a generating a visual CAPTCHA is GD, which is a graphics library that PHP uses for generating images. To check if GD is installed on your PHP web server, create a phpinfo page by creating a new file on your server with the following PHP code:

<?php phpinfo(); ?>

Next, browse to this PHP file in your web browser. There should be a section called GD. If there is no GD section then GD is not enabled on your server and you won't be able to use most CAPTCHA systems.

Also in this section you can see if FreeType support is enabled. If FreeType is enabled then you will be able to use TrueType fonts in your CAPTCHA's which will give you a much bigger range of fonts you can use to generate your CAPTCHA, thus reducing the effectiveness of scripts that attempt to automatically recognize letter and number shapes.