Self-Hosted reCAPTCHA Alternatives
reCAPTCHA is not available as a self-hosted solution but there are some alternatives for power users and business that want to host a solution on-premise. The best Self-Hosted alternative is visualCaptcha, which is both free and Open Source. If that doesn't suit you, our users have ranked more than 10 alternatives to reCAPTCHA and five of them are available as a self-hosted solution so hopefully you can find a suitable replacement. Other interesting Self-Hosted alternatives to reCAPTCHA are UniqPin, Negative Captcha, Captcheck and phpformmailer.
visualCaptcha is a configurable captcha solution, focusing on accessibility & simplicity, whilst maintaining security. It's also localizable and free, open-source, and we encourage customizations per site.
Discontinued
As from Dec 26, 2016: Please note visualCaptcha is no longer actively developed. It still works and should continue to, but it won't be improved by the initial team anymore. ...Source: https://github.com/emotionLoop/visualCaptcha/blob/master/README.md
visualCaptcha vs reCAPTCHA opinions
Free, open-source, self-hosted.
UniqPin is a free for non-commercial use service which destiny improve ability of interfaces detect a human or a computer operate with it.
A negative captcha has the exact same purpose as your run-of-the-mill image captcha: To keep bots from submitting forms. Image ("positive") captchas do this by implementing a step which only humans can do, but bots cannot: read jumbled characters from an image.
No screenshots yetEasy to use - Nothing stupid your visitors have to type before the form submits.
No screenshots yetphpformmailer vs reCAPTCHA opinions
It is not a captcha functionality
It is not a captcha functionality.