Direct Answer
A style guide (or design system) is the documented set of visual rules for a brand: color palette, typography, spacing, button styles, component patterns, and tone of voice. It keeps every page, ad, and product consistent as teams scale. Most service businesses can start with a 1-page guide; agencies and software businesses need a full system.
Voice answer (≤30 words)
“A design system documents the visual rules for a brand: color, type, spacing, components, and tone. It keeps everything consistent at scale.”
Build a Figma or Storybook design system if you ship 5+ pages a month or work with multiple designers.
Light style guide essentials: 2 fonts, 5 colors, 1 button style, 3 heading sizes. That's enough to keep most service-business marketing aligned.
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