What minimum contrast ratio does WCAG level AA require for normal-size body text?

4.5:1 is right. WCAG (Web Content Accessibility Guidelines) level AA requires a contrast ratio of 4.5:1 for normal-size text.

3:1 is the tempting wrong answer. That looser ratio applies only to large text, about 24px regular or 18.66px bold, and to UI components and graphics. 7:1 is wrong because it is the stricter AAA level for normal text.