I am trying to find an easier CAPTCHA to use with my website. I currently have reCAPTCHA but the users are struggling to get the words right the first time.
I have came across Confident CAPTCHA (here) and would like to know what you guys think about it.
Interesting captcha, I have not seen this one before.
I will try to address your second question about How safe is it?. There are no docs available or sample code to check so the analysis is based on using it a few times.
It seems like it should be reasonably secure. I see that it uses a 3rd party service, so you will rely on API calls to generate the HTML markup and validate the captcha.
In their demo, you are required to choose 4 images out of a total of 9 which means the probability of guessing the correct value is about 0.000330688% (1/9 * 1/8 * 1/7 * 1/6).
It essentially works by creating an alpha captcha code based on the sequence of images you choose. So the server generates a random challenge (cat, vehicle, drink, house) and associates each element with a random letter from the range [A-Z].
Clicking the sequence of images creates a captcha code based on the letter assigned to each image (e.g. PKIR) if cat = P, vehicle = K, drink = I, house = R that gets placed in a hidden input and submitted with the form.
Therefore the only way to pass the captcha is to come up with a code that agrees with the sequence of images on the server side.
I would conclude it is relatively secure in that there is no way to defeat the captcha solely on the client side (see this question for example). Since there is no reason for them to ever present anything related to the solution to the client (browser); it would seem logical that the only way to get the correct captcha code is to select the correct images in the correct sequence.
Conclusion:
That's my 2 cents, I hope that helps you out.