Adding CAPTCHA protection to your web site
This guide explains what CAPTCHA protection is, when to use it, and how to implement it in various programming languages.
What is a CAPTCHA?
Section titled “What is a CAPTCHA?”A CAPTCHA (Completely Automated Public Turing test to tell Computers and Humans Apart) is a test designed to determine whether a user is human or a computer. The most common CAPTCHA is an image showing obscured letters or numbers. Users must type the correct sequence to access website content or submit data. Automated bots usually cannot read these images, helping prevent misuse of your website’s resources.
The following image is an example of a common type of CAPTCHA:
When to Use CAPTCHA Protection
Section titled “When to Use CAPTCHA Protection”Consider adding CAPTCHA protection to any web page that processes user-submitted data, such as:
- Forms (email, comments, registration)
- Surveys or polls
- Pages that accept file uploads or downloads
- Any page that accepts user input
CAPTCHA Implementations
Section titled “CAPTCHA Implementations”There are several free and open-source CAPTCHA implementations depending on the programming language your website uses.
Some popular PHP CAPTCHA solutions include:
- Securimage: Easily add PHP-based CAPTCHAs. More info: phpcaptcha.org
- captchas.net: Provides CAPTCHA implementations for multiple languages including PHP. More info: captchas.net
- Google reCAPTCHA: A widely used CAPTCHA service. General info: google.com/recaptcha, PHP integration: developers.google.com/recaptcha
- Text_CAPTCHA PEAR package: Allows creating custom CAPTCHA implementations in PHP. More info: pear.php.net/package/Text_CAPTCHA
Python
Section titled “Python”- captchas.net: Also provides a Python implementation. More info: captchas.net
More Information
Section titled “More Information”For general information about CAPTCHAs, visit Wikipedia: CAPTCHA.