Rule 3.2.3
Summary
This test consists in checking whether the contrast ratio between text and its background is at least 3:1 for the
normal weighted textual elements with a font size superior to 24px.
Business description
Criterion
Test
Description
Dans chaque page web, le texte et le texte en image sans effet de graisse d’un taille restituée supérieure ou égale à 24px vérifient-ils une de ces conditions (hors cas particuliers) ?
Particular cases (criterion 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 superior to 24px and not bold
Set2
All the hidden textual elements from the DOM with a font-size superior 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 to3.
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 3.
For each element returning false in Test2, raise a MessageD
Message
MessageA : Bad Contrast
- code: BadContrast
- status: Failed
- parameter: foreground color, background color, contrast ratio, Snippet
- present in source: yes
MessageB : 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
MessageC : Not Treated Background Color
- code: NotTreatedBackgroundColor
- status: Pre-Qualified
- parameter: none
- present in source: no
MessageD : 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 superior to 24px and not bold have been found (Set1 AND Set2 are empty)
Passed
All the elements with a font-size superior 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 superior to 24px and not bold have an incorrect ratio (Test1 returns false
for at least one element)
Pre-qualified
In all other cases
Notes
- 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.