Rule 1.4.9

Summary

This test consists in detecting captcha canvas and thus defining the applicability of the test.

Human check will be then needed to determine whether the alternative is well rendered by assistive technologies.

Business description

Criterion

1.4

Test

1.4.9

Description

Pour chaque image bitmap (balise canvas) utilisée comme CAPTCHA ou comme image-test et ayant une alternative textuelle , l'alternative textuelle est-elle correctement restituée par les technologies d'assistance ?

Level

A

Technical description

Scope

Page

Decision level

Semi-Decidable

Algorithm

Selection

All the <canvas> tags of the page not within a link with a not empty content (css selector : canvas:not(a canvas):not(:matchesOwn(^\s*$)))

Set2

All the elements of Set1 identified as a CAPTCHA (see Notes for details about CAPTCHA characterisation).

Process

Test1

For each element of Set2, raise a MessageA

MessageA : Check captcha alternative restitution by assistive technologies
  • code : CheckAtRestitutionOfAlternativeOfCaptcha
  • status: Pre-Qualified
  • parameter : text tag name, snippet
  • present in source : yes

Analysis

Not Applicable

The page has no <canvas> tag with a not empty content identified as a captcha (Set2 is empty)

Pre-qualified

In all other cases

Notes

Captcha detection

An element is identified as a CAPTCHA when the "captcha" occurrence is found :

  • on one attribute of the element
  • or within the text of the element
  • or on one attribute of one parent of the element
  • or within the text of one parent of the element
  • or on one attribute of a sibling of the element
  • or within the text of a sibling of the element