A、AA、AAA：適切な目標を選ぶ

WCAG defines three conformance levels: A, AA, and AAA. Each adds more success criteria, raising the bar for how usable your site must be.

Level A is the bare minimum. Miss it and content can be completely unusable, like an image with no alt text or a control you cannot reach.

Level AA is what most teams and laws aim for. It folds in all of A plus stricter rules on contrast, focus, and resizing.

Level AAA is the strictest tier. The W3C itself says it is not a realistic goal for entire sites, so treat it as aspirational.

The tiers stack: to claim AA you must satisfy every A and every AA criterion. You cannot skip the lower level and jump ahead.

AA balances real impact against effort. It removes the barriers that block most people without demanding the rare, costly fixes that AAA asks for.

Regulations like the EU directive and most ADA settlements reference WCAG 2 Level AA. Hitting AA is how teams stay on the right side of the law.

Criterion 1.1.1 (Non-text Content) sits at level A. Every meaningful image needs a text alternative, the most fundamental rule there is.

Contrast Minimum, 1.4.3, is a level AA rule. It demands a 4.5:1 ratio for body text, a fix you simply do not get at level A.

Contrast Enhanced, 1.4.6, is AAA and asks for 7:1. Beautiful for readability, but often impossible to keep across a whole brand palette.

Commit to AA across the board, then adopt select AAA rules where they matter, like a high-contrast mode. Document exactly what you claim.

Decide which target most projects should aim for.

Three tiers stack: A is the floor, AA is the real-world goal, AAA is aspirational. Commit to AA and document any extras. Next: the new 2.2 criteria. 🎯