Business rules manual
RGAA v4.0.0
Theme 1: Images
Rule 1.1.1

Rule 1.1.1

Summary

This test consists in checking whether each <img> tag or tag with is a role="img" WAI-ARIA attribute, carrying information, owns a textual alternative.

Business description

Criterion

1.1

Test

1.1.1

Description

Chaque image (balise <img> ou balise possédant l’attribut WAI-ARIA role="img") porteuse d’information a-t-elle une alternative textuelle ?

Level

A

Technical description

Scope

Page

Decision level

Decidable with marker

Algorithm

Selection

Set1

All the <img> tags and tags with is a role="img" attribute, not within a link and not identified as captcha (see Notes about captcha detection)

Set2

All the elements of Set1 identified as informative image by marker usage (see Notes for details about detection through marker)

Set3

All the elements of Set1 identified neither as informative image, nor as decorative image by marker usage (see Notes for details about detection through marker)

Process

Tests

Test1

For each element of Set2, check whether the tag owns a textual alternative (see Notes for details about textual alternative detection).

For each occurrence of false-result of Test1, raise a MessageA.

Test2

For each element of Set3, check whether the tag owns a textual alternative (see Notes for details about textual alternative detection).

For each occurrence of true-result of Test2, raise a MessageB.

For each occurrence of false-result of Test2, raise a MessageC.

Messages

MessageA
  • code : AltMissing
  • status: Failed
  • parameter : "alt" attribute, "title" attribute, "aria-label" attribute, "computed accessible name", "src" attribute
  • present in source : yes
MessageB
  • code : CheckNatureOfElementWithTextualAlternative
  • status: Pre-Qualified
  • parameter : "alt" attribute, "title" attribute, "aria-label" attribute, "computed accessible name", "src" attribute
  • present in source : yes
MessageC
  • code : CheckNatureOfElementWithoutTextualAlternative
  • status: Pre-Qualified
  • parameter : "alt" attribute, "title" attribute, "aria-label" attribute, "computed accessible name", "src" attribute
  • present in source : yes

Analysis

Not Applicable

The page has no <img> tag and no tag with a role="img"attribute (Set1 is empty)

Passed

All <img> tags and all tags with a role="img" attribute are identified as informative, and have a textual alternative (Test1 returns true for all the elements of Set2, and Set3 is empty)

Failed

At least one <img> tag or one tag with is a role="img"attribute, identified as informative, has no textual alternative (Test1 returns false for at least one element)

Pre-qualified

In all other cases

Notes

Textual alternative detection

The textual alternative can be set by the presence of any the following elements :

  1. Text associated via the aria-labelledby WAI-ARIA attribute
  2. Presence of an aria-label WAI-ARIA attribute
  3. Presence of an alt attribute
  4. Presence of a title attribute

That order has to be respected to compute the textual alternative.

For instance, if an aria-label WAI-ARIA attribute and an alt attribute are both present, the content of the aria-label WAI-ARIA attribute is considered as the textual alternative.

Markers

Informative images markers are set through the INFORMATIVE_IMAGE_MARKER parameter.

Decorative images markers are set through the DECORATIVE_IMAGE_MARKER parameter.

The value(s) passed as marker(s) will be checked against the following attributes:

  • class
  • id
  • role

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

Files

Rule 1.1.2