10 Free CAPTCHA scripts and services for websites
This post proposes a list of ten interesting scripts and services you can use to provide protection from spam bots and ensure that only humans perform certain actions.
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1. reCAPTCHA :
reCAPTCHA is a free service which helps prevent automated abuse of your site (such as comment spam or bogus registrations) by using a CAPTCHA to ensure that only humans perform certain actions.
2. Form-to-email script protected by Captcha :
This form-to-email script is intended to collect data from an HTML form and send it to a specified email address using a CAPTCHA script to stop spam. It works with any kind of HTML form and you can use it multiple times on your pages.
OpenCaptcha is a simple web service which requires no special configurations or modules. Basic installation is cut-and-paste, and requires no ability to program image manipuation scripts. New fonts, image algorithms, and distortions applied weekly.Captchas remain the most effective, universal method of preventing automated spam currently available on the web. While services like akismet and linksleeve provide valuable protection, they are dependent upon widespread adoption to be successful.
ProtectWebForm is a service to add CAPTCHA images and audio files on your website. You have to create an account, generate your CAPTCHA type with all the desired parameters and include it on your web pages.You can also use it on your WordPress template with this plugin.
Securimage is an open-source free PHP CAPTCHA script for generating complex images and CAPTCHA codes to protect forms from spam and abuse. It can be easily added into existing forms on your website to provide protection from spam bots.
Cryptographp is a PHP script for generate captchas. Cryptographp limit the robots bombarding spams and automating the forms: spaces members subscriptions, guestbooks, forums… This script is free and does not use any database. It is compatible with PHP >= 4.3.0
WebSpamProtect allows you to instantly add verification image (CAPTCHA) to your web site and protect your forms against spam robots. In order to protect your web form, our system requires that you install a small piece of code onto your web page. Our code requires that your web site support PHP, Perl, ASP or ASP.NET.
CaptchasDotNet.asp. allows you to instantly add verification image (CAPTCHA) to your web site and protect your forms against spam robots. In general the process of using CAPTCHA can be divided into two stages. First you have to query the user for the CAPTCHA, on that page you also usually let the user input the data, which has to be protected, e.g. blog entries.
captchas.net provides CAPTCHA images and audio files you can use in html-forms. To use this technology, your web pages have to be generated dynamically in any programming language PHP, ASP, Perl, Python, JSP, Ruby.