ガイド
WCAGコントラスト比の基本（難しい用語なし）
コントラスト比の意味とAA/AAA基準を実務UIで使う方法をわかりやすく解説します。
コントラスト比は数字だけだと分かりにくいものです。このガイドでは実務で使える形に整理します。
What a contrast ratio represents
It compares how different a text color is from its background.
Higher ratios generally mean easier reading.
AA and AAA in simple terms
AA is the common practical baseline for most web interfaces.
AAA is stricter and useful where maximum readability is needed.
Normal text vs large text
Large text can pass at lower ratios than normal body text.
Always classify text size correctly before deciding pass/fail.
How to apply this in a workflow
Check planned color pairs before development.
Retest final UI states after implementation.
When to read this
- Starting accessibility reviews.
- Training designers and developers.
- Creating color QA checklists.
Use ratios as a decision tool
You do not need to memorize every rule. Use a checker and know which threshold applies to your text size.