Design System
A design system is the coherent set of components, rules, and tokens (colors, typography, spacing) that keeps a site visually unified.
A design system centralizes visual decisions: color palette, type scale, button style, spacing. Every component on the site draws from these shared rules.
On a growing site, it prevents inconsistency: two different buttons, three shades of blue. It also speeds up building new pages, since each building block is already defined.