POUR is the acronym for the four foundational principles of WCAG: Perceivable, Operable, Understandable and Robust. Content must be perceivable through the senses, the interface must be operable by every input method, information must be understandable, and the code must work reliably with assistive technologies. All guidelines and success criteria in WCAG are organized under these four principles.
Each of the four principles answers a question. Perceivable: can the user take in the content with at least one sense (alt text for images, captions for video, sufficient color contrast)? Operable: can the interface be used not only with a mouse but also with a keyboard and other input methods, and is the user given enough time? Understandable: is the text readable, are pages predictable, are forms designed to prevent mistakes? Robust: can the code be interpreted reliably by the browsers and assistive technologies of today and tomorrow?
POUR is the framework of WCAG: the standard defines these four principles at the top, with guidelines under each principle and testable success criteria under each guideline. A site's conformance is measured through those criteria, not through the principles themselves. Even so, the principles serve as a compass in daily work: asking 'is it perceivable, operable, understandable, robust' while designing a new component catches most problems before you ever open the criteria list. On the audit side, POUR is also a useful mental map: grouping automated scan findings under the four principles clarifies where issues cluster and where to start.
Frequently asked questions
What are the POUR principles?
POUR stands for the four foundational principles of WCAG: Perceivable (content must be available to at least one sense, for example alt text for images), Operable (the interface must work with every input method, including the keyboard), Understandable (text and behavior must be clear and predictable) and Robust (code must be reliably interpretable by assistive technologies). Every success criterion in WCAG sits under one of these four principles.
Is following the POUR principles enough for WCAG conformance?
The principles give direction, but conformance is not measured against them. WCAG conformance is determined by meeting the testable success criteria at the targeted level (A, AA or AAA); the principles are the framework above those criteria. The right approach is this: use POUR as a compass during design and development, and verify conformance criterion by criterion through automated scanning and manual testing.
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