WCAG 2.x Principles, Guidelines, and Success Criteria
WCAG 2.x is organized into four principles-Perceivable, Operable, Understandable, Robust-then guidelines (non-testable design objectives) and success criteria (testable requirements). Each SC has a level: A (minimum), AA (standard procurement target), AAA (enhanced). WCAG 2.2 adds criteria such as 2.4.11 Focus Not Obscured (Minimum) AA, 2.5.7 Dragging Movements AA, 2.5.8 Target Size (Minimum) AA at 24×24 CSS pixels, 3.3.7 Redundant Entry A, and 3.3.8 Accessible Authentication (Minimum) AA.
Conformance rules
A conformance claim requires full pages, complete processes, only accessibility-supported technologies, and non-interference. AA conformance means all Level A and AA criteria are met. "Partially conformant" is not a WCAG conformance state.
Worked example
A modal dialog closes and focus drops to the top of the page. Relevant SC: 2.4.3 Focus Order (focus order must preserve meaning and operability) and 2.4.7 Focus Visible. The fix is to return focus to the triggering button. Reasoning: keyboard and screen reader users lose context; the dialog must also trap focus while open and be dismissible with Escape (2.1.2 No Keyboard Trap allows standard exit).
Traps
Calling guidelines testable; mixing SC numbers and levels; assuming AAA is required; claiming conformance for a component rather than a page; forgetting that "accessibility-supported" is part of conformance; and treating 2.2 additions as optional when the target is WCAG 2.2 AA.