21 Free CAPTCHA Sources

Here is a collection of free CAPTCHA scripts and services than you can easily integrate into your website using PHP or JavaScript:

1. PHP CAPTCHA Library for reCAPTCHA

http://recaptcha.net/plugins/php

2. Ajax Fancy Captcha – jQuery Plugin

http://www.webdesignbeach.com/beachbar/ajax-fancy-captcha-jquery-plugin

3. Securimage (PHP)

http://www.phpcaptcha.org

4. JCaptcha (Java)

The open source java framework for captcha definition and integration
http://jcaptcha.sourceforge.net/

5. The Captcha

http://www.thecaptcha.com/

6. 3D Captcha

http://www-personal.umich.edu/~mressl/3dcaptcha/

7. ASSIRA

http://research.microsoft.com/en-us/um/redmond/projects/asirra/

8. Captchas.net – Free CAPTCHA Service

http://captchas.net/

9. Visual and Audio PHP CAPTCHA Generation Class

http://www.ejeliot.com/pages/php-captcha

10. freeCap PHP CAPTCHA

http://www.puremango.co.uk/2005/04/php_captcha_script_113/

11. Cool PHP CAPTCHA

http://code.google.com/p/cool-php-captcha/

12. Quick CAPTCHA 1.0 (PHP)

http://www.web1marketing.com/resources/tools/quickcaptcha/

13. Jcap (Javascript)

http://www.archreality.com/jcap/

14. Simple Javascript CAPTCHA

http://sourcefirst.wordpress.com/2007/05/02/simple-javascript-captcha/

15. CAPTCHA Service – Web Form Spam Protection

http://webspamprotect.com/

16. cryptograPHP

http://www.captcha.fr/

17. Free CAPTCHA Form-To-Email Script

http://www.snaphost.com/captcha/

18. hoomanTest: A Mootools Bot Filtering CAPTCHA Class

http://fragged.org/dev/hOOmanTest_captcha_for_mootools.php

19. Simple PHP-GD CAPTCHA Image

http://www.php-help.ro/php-tutorials/simple-php-gd-capcha-image/

20. Simple AJAX CAPTCHA

http://blog.smileylover.com/simple-ajax-captcha/

21. AJAX CAPTCHA 1.0

http://webscripts.softpedia.com/script/PHP-Clases/AJAX-CAPTCHA-50370.html

Enjoy!