Brand guidelines (brand book)
The document telling everyone else how to use your identity correctly, so the brand survives contact with other people.
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What it is
Brand guidelines are the document that tells everyone who is not you how to use the identity. The standard contents: the logo suite and lockups, clear space and minimum size, color values in HEX, RGB, CMYK, and Pantone, typefaces with a size hierarchy, imagery direction, a misuse page, and often voice and worked examples. The 1975 NASA Graphics Standards Manual is the genre's greatest hit.
You need one the moment a stranger touches the logo: a printer, a freelancer, a conference organizer, a new hire, a partner building a co-branded page. Ten honest pages people actually read beat ninety pages nobody opens, so write for the person in a hurry.
Gotcha: guidelines rot when they live only as a PDF attached to an old email. Publish them as a page with copyable hex values, downloadable vector artwork, and a version date. And give every rule a one-line reason, because a rule someone understands is the only kind that survives a deadline.
Ask AI for it
Using the attached logo suite, verified palette [HEX, RGB, CMYK, AND PANTONE VALUES], licensed fonts [NAMES AND WEIGHTS], imagery references, voice guide, measured minimum sizes, and asset URL [URL], assemble lean, skimmable brand guidelines with these sections: (1) logo suite showing primary, secondary, icon-only, and reversed variants, (2) clear space and minimum size with dimension diagrams, (3) color palette with the supplied values plus approved background pairings, (4) typography with the supplied typefaces, weights, and a heading-to-caption size scale, (5) imagery and illustration direction with do and don't examples built from the supplied references, (6) a misuse page covering stretching, recoloring, rotating, adding shadows, and busy backgrounds, (7) voice rules drawn from the supplied guide with sample sentences. Copy every supplied specification exactly, give every rule a one-line reason, keep it under 20 pages, and end with the asset URL. Flag anything I did not supply as missing instead of inventing a value.