What is WCAG (Web Content Accessibility Guidelines)?

WCAG (Web Content Accessibility Guidelines) is the internationally recognized standard, published by the W3C, that defines how to make web content accessible to people with disabilities, organized around four principles and three conformance levels (A, AA, AAA).

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IN DEPTH

In depth.

WCAG is the reference QA uses to test and certify accessibility. Its guidelines are organized under four principles, remembered as POUR: Perceivable (users can perceive the content, e.g., text alternatives for images, captions), Operable (the interface can be operated, e.g., full keyboard access, no keyboard traps), Understandable (content and operation are clear, e.g., readable text, predictable behavior, helpful errors), and Robust (content works with assistive technologies and adapts as they evolve, e.g., valid markup and correct ARIA).

Each guideline has testable success criteria assigned a conformance level: A (minimum), AA (the common legal and practical target), and AAA (highest, rarely required wholesale). Most organizations aim for WCAG AA, which is referenced by laws and policies (such as the ADA in practice, the European Accessibility Act, and Section 508).

Testing against WCAG combines automated tools (axe, Lighthouse, WAVE) that catch a meaningful subset of issues (missing alt text, contrast, ARIA misuse) with essential manual testing, keyboard-only navigation, screen-reader use, and human judgment about whether content actually makes sense, because automation alone cannot evaluate things like logical reading order or meaningful link text. Conformance to WCAG is a form of conformance testing.

WHY IT MATTERS

Why interviewers ask about this.

WCAG is the backbone of accessibility testing interviews. Knowing the POUR principles, the A/AA/AAA levels (and that AA is the usual target), and that automated tools only catch part of the picture, manual and assistive-tech testing are essential, shows you can test accessibility credibly, not just run a scanner.

EXAMPLE

Example scenario.

A team targets WCAG 2.2 AA. Automated scans (axe, Lighthouse) flag low color contrast and missing form labels. Manual testing then reveals issues automation missed: a modal that traps keyboard focus and images whose alt text is unhelpful. Fixing all of them brings the site to AA conformance, satisfying both users and legal requirements.

TIP

Interview tip.

Define WCAG as the W3C standard for web accessibility, structured around the POUR principles (Perceivable, Operable, Understandable, Robust) with conformance levels A, AA, AAA, where AA is the usual target. Stress that testing needs both automated tools and manual/assistive-tech testing, since automation catches only part of the criteria.

FAQ

Frequently asked questions.

What are the POUR principles of WCAG?

POUR stands for Perceivable (users can perceive the content, e.g., text alternatives, captions), Operable (the interface can be operated, e.g., keyboard access), Understandable (content and operation are clear and predictable), and Robust (content works reliably with assistive technologies via valid markup and correct ARIA). All WCAG guidelines fall under these four.

What WCAG level should you target?

AA is the common, practical target referenced by most laws and policies (and stricter than A, the minimum). AAA is the highest level but is rarely required wholesale because some criteria are impractical for all content. Most organizations aim for WCAG 2.1 or 2.2 AA conformance.