Love them or hate them, image captchas are everywhere. From sign-ups forms to comment posting, these automatically generated images help combat spam and brute-force attacks.
In this post, we’ll take a look at the top 10 Free PHP Image Captcha Scripts ranked by the following criterias:
- Customization – ability to customize the captchas look and feel (e.g custom fonts, background, word-lists).
- Integration – how easy is it to add the image captchas to existing forms.
- Accessibility – support for visually impared (e.g ability to stream audio version of captchas)
- Speed – how fast are images generated? (e.g use of caching)
Securimage is an open-source free PHP CAPTCHA class for generating CAPTCHA images. It has support for streaming MP3 audio of the code to the user’s browser with Flash. You can specify custom TTF fonts, set character distortion, custom colors, backgrounds and even use your own worldlists or custom character sets.
2. Open Captcha
OpenCaptcha is a php script designed to dynamically create a captcha image in .png form. It uses a randomly chosen background to start with, then chooses a random string of a randomly chosen length, color, size, font, and orientation. With OpenCaptcha, you can easily use your own custom backgrounds and fonts to make it fit in better with your overall site design.
Captcher is a PHP script that generates and verifies captchas. Captcher generates captcha images on the fly, and thus does not need to be able to cache them. It can generate captchas of any length, and can have its fonts and colors configured as desired. (Required GD library and mySQL)
4. Captcha ZDR
Captcha ZDR is a simple, complete and powerfull captcha tool written in PHP for protecting your web FORMS from spammers. It offers several methods of captcha protection, different fonts, string protection, calculation protection (sum and deduction), noise in image, string symbols are hard for reading from spamer machines.
submitThroughImage is a lightweight PHP image captcha script that produces an image with a randrom string and a form input. The random generated image string will be matched against a session variable or against a file store on your server. It has support for custom TTF fonts, colors and background.
HKCaptcha is yet another captcha implementation in PHP. This one is written with the current state of captcha-defeating research in mind. Apart from a mathematical letter distortion algorithm that is more than just rotating the letters, the clutter is designed to make segmentation of the image into separate letter glyphs hard to do automatically.
PHP Captcha Security Images generates images (known as “Captcha’s”), which contain security codes used for protecting a form from spam bots. By encoding a ‘password’ inside an image and asking the user to re-enter what they see you can verify the user is a human and not automated software submitting your form.
freeCap is a GPL CAPTCHA script to stop spam. There are a whole load of tweakable options: multiple GD fonts, colours, backgrounds, obfuscation options etc. freeCap can output as JPG, PNG or GIF, has brute force protection, is open source and is totally self-contained – no need for SQL databases, PEAR, or anything beyond PHP and GD!
PhpCaptcha is a library for generating visual and audio CAPTCHAs (completely automated public Turing test to tell computers and humans apart). It supports multiple random TrueType fonts, character rotation, font size selection, custom background and character set selection.
10. Custom CAPTCHA
Custom CAPTCHA is a PHP class that can be used to display images for CAPTCHA validation. The text is rendered over a given obfuscation image. The length, font and size of the text is configurable. he validation text is stored in a session variable for posterior validation. The validation image format can be either GIF, JPEG or PNG.
For more PHP Image Captchas, visit our Security Systems category. If you have suggestions for other scripts that should have made it to this list, please leave a comment to this post. We also welcome suggestions for future Top 10 scripts lists you’d like us to cover.