Relative Font Sizing

The practice of specifying text sizes using relative units (such as em, rem, or percentages) rather than absolute units (such as pixels or points), allowing text to scale when users adjust their browser or system font size settings. Relative font sizing is an important accessibility technique because users with low vision or reading difficulties often rely on browser zoom or text size controls to make content readable. When fonts are defined with absolute sizes, changing browser settings has no effect on the text, creating a significant barrier. WCAG requires that text can be resized up to 200% without loss of content or functionality, which is most reliably achieved through relative sizing.