What Is WCAG
The Web Content Accessibility Guidelines (WCAG) are an internationally recognized standard published by the World Wide Web Consortium (W3C). They define how to make web content more accessible to people with disabilities, including visual, auditory, motor, and cognitive impairments. WCAG is the technical standard referenced by most accessibility legislation worldwide.
Four Principles: POUR
WCAG is organized around four foundational principles. All content must be:
- Perceivable — Information must be presentable to users in ways they can perceive (Principle 1)
- Operable — User interface components must be operable by all users (Principle 2)
- Understandable — Information and operation must be understandable (Principle 3)
- Robust — Content must be robust enough to be interpreted by assistive technologies (Principle 4)
Conformance Levels
| Level | Description | Criteria Count |
|---|---|---|
| A | Minimum level of accessibility — essential requirements | 32 |
| AA | Standard target for most legislation — addresses the most common barriers | 24 |
| AAA | Enhanced accessibility — not typically required by law | Not tracked |
Crucible Scan evaluates all 56 Level A and AA criteria from WCAG 2.2. Level AA conformance (which includes all Level A criteria) is the standard target for ADA, Section 508, EAA, and AODA compliance.
Automated vs Manual Testing
Not all WCAG criteria can be fully evaluated by automated tools. Crucible Scan classifies each criterion by testability:
- Automated — Fully testable by the scanner (e.g., checking if images have alt attributes)
- Hybrid — Partially automated with manual verification needed (e.g., checking alt text quality)
- Manual — Requires human evaluation (e.g., testing keyboard navigation flow)
The scanner runs 15 automated tests that cover the criteria most amenable to machine analysis. Criteria requiring manual evaluation are tracked as “Not Evaluated” until you provide manual evidence through the review workflow.