Glossary · Accessibility term
POUR
POUR is the field's shorthand for WCAG's four principles, which are Perceivable, Operable, Understandable and Robust. Every guideline and every rule in the standard sits under exactly one of them, so it is the fastest way to hold the whole thing in your head. Can somebody take the information in, can they work the controls, can they follow what is happening, and will it keep working with the software they use? Two things about the acronym are worth knowing. It appears nowhere in the standard itself, which always names the four in full, so it is a teaching device rather than something you can point at in the specification. And the four are nothing like equal. Perceivable holds 29 criteria and Operable 34, Understandable has 21, and Robust has two.
In practice
The lopsidedness is the interesting part and it explains a lot. Robust has one guideline and two criteria, and between them they account for a large share of what breaks on real sites. That is where names, roles and states live. Two rules, and they decide whether a custom component exists at all as far as assistive technology is concerned.
It is the top of a four-layer stack rather than a list on its own. Principles state the goals, guidelines group the rules under those goals, success criteria are the testable statements, and the techniques below them are advice on how to pass. Only the first three layers are binding and only the third is testable, which is why an argument about whether something meets a principle is never an argument about conformance. The criteria are not the whole of a conformance decision, though. Five conformance requirements sit beside them and get assessed alongside them.
Use it as a diagnostic rather than a checklist. Ask which of the four questions a failure answers no to, because that tells you who is affected and roughly what the fix looks like. Plenty of failures answer no to more than one, since a single defect can break several criteria at once. A missing caption and a missing accessible name are both failures and they are not the same kind of problem.
Why it matters
The acronym is how the standard becomes memorable. It also explains why an audit report is organised the way it is, and why a clean result in one principle tells you almost nothing about the others. Where it misleads is if you read it as four equal quarters. Level A and AA together come to 55 criteria, spread 20 in Perceivable, 20 in Operable, 13 in Understandable and 2 in Robust. Planning work by principle means planning very different amounts of work. Count before you plan.
The four questions
Can they perceive it, can they operate it, can they understand it, and is it robust enough for the software they use? Every one of WCAG 2.2's 86 criteria sits under one of those. The fourth is the one people forget, because it is only two rules, and it is where a beautiful, usable interface built out of divs reaches a screen reader as a stack of things with no name and no kind.
Where this shows up on the site
Related terms
- PerceivablePerceivable is the first of WCAG's four principles, and the standard states it as information and user interface components being presentable in ways people can perceive.
- OperableOperable is the second WCAG principle, and its one-line statement is that user interface components and navigation must be operable.
- UnderstandableUnderstandable is the third of WCAG's four principles, and it splits in two the way its own sentence does.
- RobustRobust is the fourth of WCAG's four principles, and it asks that content be built well enough for a wide variety of user agents, including assistive technology, to interpret it.
- WCAGWCAG is the international standard for web accessibility, published by the W3C.
- GuidelineA guideline is the middle layer of WCAG, and WCAG 2.2 has 13 of them sitting between the four principles and the rules anybody is ever tested against.
Knowing the word is the easy part.
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