None of them is usable by deafblind people, and all of them are difficult for people with cognitive disabilities. Meanwhile bots are excellent at solving them.
@downey One reason I'm asking this because I'm concerned about the "CAPTCHAs are entirely unacceptable from an accessibility POV" stuff I'm seeing recently. Realistically, CAPTCHAs aren't going away. It seems wiser to acknowledge the ones that try to be accessible than to tar and feather them with the others. Otherwise what incentive does any CAPTCHA developer have to make an effort toward accessibility?
@downey The experience is definitely degraded when that happens (for both disabled and non-disabled users!), but it appears that Google has put a great deal of effort into ensuring that even when that happens it is still accessible. Ref: https://support.google.com/recaptcha/answer/6175971
@jik I don't know of any studies, but the problem with their "invisible" product is that it's only invisible if it has n inference (true or false) that the user is human. So it reverts to the same accessibility challenges as the others in a portion of visits.
If anyone knows of any concrete evidence that Google's Invisible reCAPTCHA adversely impacts people with disabilities more than others, I'd be grateful if you could share it with me. I searched but could not find any; on the contrary, I found at least one study showing that Invisible reCAPTCHA is equally usable for disabled and non-disabled people. To be clear, I'm not looking for theoreticals, I'm looking for concrete evidence one way or the other. Thanks. #accessibility