A style guide is a document that defines rules for consistent brand presentation. It covers logo usage, color codes, typography, spacing, imagery, and tone of voice. The goal is simple: anyone producing materials for a brand should be able to follow the same rules and get the same look. Without a style guide, a company's website, packaging, and social media drift apart until they no longer feel related.

Style guides range from a single page to a hundred-page manual. A small startup might document five colors and two typefaces. A global brand like Coca-Cola or NASA maintains extensive guidelines covering everything from minimum logo size to approved photography styles. Digital design systems like Google's Material Design and Apple's Human Interface Guidelines serve a similar function for product teams, specifying components, interactions, and accessibility standards.

What a style guide covers

• Logo variations and clear space rules.
• Color palette with exact codes.
• Typeface families, sizes, and weights.
• Imagery, iconography, and tone of voice.

A style guide is a living document. Brands update it as they evolve. The best ones are practical, not precious. They help people make decisions quickly, and they leave room for the occasional exception.