Business rules manual
RGAA v4.1.2
Theme 3: Colours
Rule 3.2.1

Rule 3.2.1

Summary

This test consists in checking whether the contrast ratio between text and its background is at least 4.5:1 for the normal weighted, under 24px sized, textual elements

Business description

Criterion

3.2

Test

3.2.1

Description

Dans chaque page web, le texte et le texte en image sans effet de graisse d’une taille restituée inférieure à 24px vérifient-ils une de ces conditions (hors cas particuliers)?

  • Le rapport de contraste entre le texte et son arrière-plan est de 4.5:1, au moins
  • Un mécanisme permet à l’utilisateur d’afficher le texte avec un rapport de contraste de 4.5:1, au moins.

Cas particuliers (3.2)

Dans ces situations, les critères sont non applicables pour ces éléments

  • Le texte fait partie d’un logo ou d’un nom de marque d’un organisme ou d’une société
  • Le texte ou l’image de texte est purement décoratif
  • Le texte fait partie d’une image véhiculant une information mais le texte lui-même n’apporte aucune information essentielle
  • Le texte ou l’image de texte fait partie d’un élément d’interface sur lequel aucune action n’est possible (par exemple un bouton avec l’attribut disabled).

Level

AA

Technical description

Scope

Page

Decision level

Decidable

Algorithm

Selection

Set1

All the textual elements from the DOM with a font-size inferior or equals to 24px and not bold

Set2

All the hidden textual elements from the DOM with a font-size inferior or equals to 24px and not bold

Set3

All the <img> tags

Process

Test1

For each element of Set1, the contrast ratio is computed (regarding the contrast ratio definition) to check whether it is superior to 4.5.

For each element returning false in Test1, if the ALTERNATIVE_CONTRAST_MECHANISM is set to true by the user, raise a MessageA, raise a MessageB instead.

If an element has a contrast ratio that cannot be determined (background defined with an image or a gradient), raise a MessageC

Test2

For each element of Set2, the contrast ratio is computed (regarding the contrast ratio definition) to check whether it is superior to 4.5.

For each element returning false in Test2, raise a MessageD

Messages

Message1: Bad Contrast

  • code: BadContrast
  • status: Failed
  • parameter: foreground color, background color, contrast ratio, Snippet
  • present in source: yes

Message2: Bad Contrast But Alternative Contrast Mechanism Present On Page

  • code: BadContrastButAlternativeContrastMechanismOnPage
  • status: Pre-Qualified
  • parameter: foreground color, background color, contrast ratio, Snippet
  • present in source: yes

Message3: Not Treated Background Color

  • code: NotTreatedBackgroundColor
  • status: Pre-Qualified
  • parameter: none
  • present in source: no

Message4: Bad Contrast on Hidden Element

  • code: BadContrastHiddenElement
  • status: Pre-Qualified
  • parameter: foreground color, background color, contrast ratio, Snippet
  • present in source: yes

Analysis

Not Applicable

No element with a font-size inferior or equals to 24px and not bold have been found (Set1 AND Set2 are empty)

Passed

All the elements with a font-size inferior or equals to 24px and not bold have a correct ratio and the page contains no images (Test1 returns true for all elements AND Set2 AND Set3 are empty)

Failed

At least one element with a font-size inferior or equals to 24px and not bold have an incorrect ratio (Test1 returns false for at least one element)

Pre-qualified

In all other cases

Notes

  1. The background color ("background" css property), the font color ("color" css property), the font size ("font-size" css property) and the font weight ("font-weight" css property) are retrieved while fetching the page, through a javacript script. Each html element is parsed to extract these info, as well as its visibility ("display" css property equals to none or "visibility" css property equals to hidden) and whether it is a textual node.

Files

Rule 3.1.6Rule 3.2.2