Accessible Web Content (WCAG)
What to know
WCAG is organized around four principles (POUR) and three conformance levels (A, AA, AAA). Candidates must know success criteria by number and intent. High-yield items: 1.1.1 non-text content alternatives; 1.2.x captions, audio description, transcripts; 1.3.1 info and relationships; 1.4.1 use of color; 1.4.3 contrast (4.5:1 normal, 3:1 large); 1.4.11 non-text contrast (3:1); 2.1.1 keyboard; 2.4.1 bypass blocks; 2.4.3 focus order; 2.4.7 focus visible; 2.5.8 target size (24×24 CSS px, AA in 2.2); 3.3.1/3.3.2 error identification and labels; 4.1.2 name, role, value.
Traps
- Confusing 1.4.3 (text contrast) with 1.4.11 (UI/icon contrast).
- Assuming AAA is expected; it is rarely required.
- Forgetting that "large text" means 18pt or 14pt bold (approx. 24px/18.66px).
- Treating captions and transcripts as interchangeable; captions are synchronized, transcripts are not.
Rule of thumb
Before answering, identify the principle and the level. If a criterion number is cited, verify it matches the described behavior.
Worked example
A button has a 2.9:1 border against its background. 1.4.11 requires 3:1 for non-text UI components, so this fails AA. Increasing the border contrast to 3:1 or more resolves it.