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CAPTCHA Note Update


The Current Document

Revisions Needed to Current CAPTCHA Note

New Information & Research

Research: Surveys

Usage Guides

CAPTCHA "Busting" Tools

Note: Services are listed alphabetically. Inclusion or exclusion from this list does not imply anything other than the compiler's ignorance.

CAPTCHA alternatives

CAPTCHA Email Threads (post CAPTCHA Note Release)

CAPTCHA Threads on Protocols & Formats Working Group List (w3c-wai-pf)

NOTE: The emailing list's archives are member-confidential.

PF Thread 1: CAPTCHA combinatorics

CAPTCHA Implementors' Threads on WAI-XTech

NOTE: The emailing list's archives are public.

WAI-XTech Thread 1: "reCAPTCHA" and "captcha workarounds"

WAI-XTech Thread 2: Progress Report on CAPTCHA (July 2007)

WAI-XTech Thread 3: reCAPTCHA Imnplementation Problems (July 2007)

WAI-XTech Thread 4: reCAPTCHA: audio alternativess and audio formats (July 2007)

WAI-XTech Thread 5: note: two-level nav in WAI-ARIA (was CAPTCHA Implementation Problems)


WAI-XTech Thread 7: wikimedia CAPTCHA issue report and responses (August 2007)

WAI-XTech Thread 8: Getting Past Google's CAPTCHA (September 2008)

Targetted Discussion Threads on WAI-XTECH (

WAI-XTech Thread 2.1: Authentification (March 2010)

CAPTCHA Threads on HTML Accessibility Task Force List (public-html-a11y)

HTML TF Thread 1: keep CAPTCHA out of HTML5 (March 2010)

HTML TF Thread 2: CAPTCHA alternatives/pitfalls

HTML TF Thread 3: Authentification (was: CAPTCHA alternatives/pitfalls) March 2020

NOTE: This thread has been moved to

HTML TF Thread 4: Draft CAPTCHA Survey