The 4 WCAG principles
Perceivable, operable, understandable, robust: the four WCAG principles, the guidelines filed under each and the habit of tying a real defect to the principle it breaks.
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Each topic is weighted the way the exam weighs it.
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A few cards from the deck
WCAG: what is it?
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International W3C recommendations on how to make web content accessible, organised into principles, guidelines and testable success criteria.
The acronym stands for Web Content Accessibility Guidelines. Versions 2.1 and 2.2 hold 13 guidelines spread under four principles; each guideline breaks down into criteria that can be checked.
A site's images have no
altattribute: a blind person cannot tell what they show. Which principle is broken?- Perceivable
- Operable
- Understandable
- Robust
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Perceivable
The information reaches none of the user's senses: this is the text alternatives guideline, under "perceivable". The image does not block action or understanding: it fails perception.
The four WCAG principles are remembered by the acronym …: Perceivable, Operable, Understandable, Robust.
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The four WCAG principles are remembered by the acronym POUR: Perceivable, Operable, Understandable, Robust.
Every success criterion is filed under one of them: if a defect fits none, it was probably described badly.
Web accessibility: what is it?
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The quality of a site that everyone can perceive, operate and understand, including a person who is blind, deaf, unable to use a mouse or living with a cognitive impairment.
It does not concern only a minority: a user in sunlight on a phone, with an arm in plaster or on a slow connection benefits from the same fixes.
A submenu only opens on mouse hover: it cannot be reached with the Tab key. Which principle is broken?
- Perceivable
- Operable
- Robust
- Understandable
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Operable
The content is visible and clear, but it cannot be acted on without a mouse. Every function must work from the keyboard: the "keyboard accessible" guideline, under "operable".