Editing CAPTCHA (section)

== Accessibility ==
{{See also|Web accessibility}}
[[File:FancyCaptcha screenshot.png|left|thumb|260px|Many websites require typing a CAPTCHA when creating an account to prevent spam. This image contains a user trying to type the CAPTCHA word "sepalbeam" to protect against automated spam.]]

CAPTCHAs based on reading text—or other visual-perception tasks—prevent [[blindness|blind]] or [[visual impairment|visually impaired]] users from accessing the protected resource.<ref name="w3c_inaccessibility">{{cite web |url=http://www.w3.org/TR/turingtest/ |title=Inaccessibility of CAPTCHA |date=2005-11-23 |access-date=2015-04-27 |publisher=[[W3C]] |author=May, Matt |archive-date=21 May 2012 |archive-url=https://web.archive.org/web/20120521023537/http://www.w3.org/TR/turingtest/ |url-status=live }}</ref><ref>{{cite magazine |author=Shea, Michael |url=http://www.theskinny.co.uk/tech/features/captcha-spambots-ebooks-and-the-turing-test |title=CAPTCHA: Spambots, eBooks and the Turing Test |date=19 November 2015 |magazine=[[The Skinny (magazine)|The Skinny]] |access-date=9 January 2016 |archive-date=27 January 2016 |archive-url=https://web.archive.org/web/20160127043239/http://www.theskinny.co.uk/tech/features/captcha-spambots-ebooks-and-the-turing-test |url-status=live }}</ref> Because CAPTCHAs are designed to be unreadable by machines, common [[assistive technology]] tools such as [[screen readers]] cannot interpret them. The use of CAPTCHA thus excludes a small percentage of users from using significant subsets of such common Web-based services as PayPal, Gmail, Orkut, Yahoo!, many forum and weblog systems, etc.<ref>{{Cite web|title=Inaccessibility of CAPTCHA|url=https://www.w3.org/TR/2019/NOTE-turingtest-20191209/Overview.html|access-date=2020-10-31|website=www.w3.org|archive-date=4 November 2020|archive-url=https://web.archive.org/web/20201104011109/https://www.w3.org/TR/2019/NOTE-turingtest-20191209/Overview.html|url-status=live}}</ref> In certain jurisdictions, site owners could become targets of litigation if they are using CAPTCHAs that discriminate against certain people with disabilities. For example, a CAPTCHA may make a site incompatible with [[Section 508]] in the United States.

CAPTCHAs do not have to be visual. Any hard [[artificial intelligence]] problem, such as [[speech recognition]], can be used as CAPTCHA. Some implementations of CAPTCHAs permit users to opt for an audio CAPTCHA, such as reCAPTCHA, though a 2011 paper demonstrated a technique for defeating the popular schemes at the time.<ref>{{cite book|last1=Bursztein|first1=Elie|first2=Romain|last2=Beauxis|first3=Hristo|last3=Perito|first4=Daniele|last4=Paskov|last5=fabry|first5=Celine|last6=Mitchell|first6=John C.|title=2011 IEEE Symposium on Security and Privacy |chapter=The Failure of Noise-Based Non-continuous Audio Captchas |pages=19–31|year=2011|chapter-url=https://www.elie.net/publication/the-failure-of-noise-based-non-continuous-audio-captchas|doi=10.1109/SP.2011.14|isbn=978-1-4577-0147-4|s2cid=6933726|access-date=5 April 2016|archive-date=16 April 2016|archive-url=https://web.archive.org/web/20160416221427/https://www.elie.net/publication/the-failure-of-noise-based-non-continuous-audio-captchas|url-status=live}}</ref>

A method of improving CAPTCHA to ease the work with it was proposed by ProtectWebForm and named "Smart CAPTCHA".<ref>{{cite web|date=2006-10-08|title=Smart Captcha|url=http://www.protectwebform.com/smartcaptcha|url-status=dead|archive-url=https://web.archive.org/web/20161104163541/http://protectwebform.com/smartcaptcha|archive-date=2016-11-04|access-date=2017-09-15|publisher=Protect Web Form .COM}}</ref> Developers are advised to combine CAPTCHA with JavaScript. Since it is hard for most bots to parse and execute JavaScript, a combinatory method which fills the CAPTCHA fields and hides both the image and the field from human eyes was proposed.<ref>{{Cite web |title=Invisible reCAPTCHA |url=https://developers.google.com/recaptcha/docs/invisible |access-date=2022-10-28 |website=Google Developers |language=en |archive-date=16 January 2020 |archive-url=https://web.archive.org/web/20200116133416/https://developers.google.com/recaptcha/docs/invisible |url-status=live }}</ref>

One alternative method involves displaying to the user a simple mathematical equation and requiring the user to enter the solution as verification. Although these are much easier to defeat using software, they are suitable for scenarios where graphical imagery is not appropriate, and they provide a much higher level of accessibility for blind users than the image-based CAPTCHAs. These are sometimes referred to as MAPTCHAs (M = "mathematical"). However, these may be difficult for users with a cognitive disorder, such as [[dyscalculia]].<ref>{{Cite web |title=Inaccessibility of CAPTCHA |url=https://www.w3.org/TR/turingtest/Overview.html |access-date=2022-10-27 |website=www.w3.org |archive-date=27 October 2022 |archive-url=https://web.archive.org/web/20221027095016/https://www.w3.org/TR/turingtest/Overview.html |url-status=live }}</ref>

Challenges such as a logic puzzle, or trivia question can also be used as a CAPTCHA. There is research into their resistance against countermeasures.<ref>{{Cite journal |last1=Gao |first1=Song |last2=Mohamed |first2=Manar |last3=Saxena |first3=Nitesh |last4=Zhang |first4=Chengcui |date=June 23, 2017 |title=Emerging-Image Motion CAPTCHAs: Vulnerabilities of Existing Designs, and Countermeasures |journal=IEEE Transactions on Dependable and Secure Computing |type=Website |language=English |edition=1st |volume=16 |issue=6 |pages=1040–1053 |doi=10.1109/TDSC.2017.2719031 |s2cid=41097185 |issn=1941-0018 |doi-access=free }}</ref>