Product Writing Style Guide Template

A style guide covers mechanical rules: capitalization, punctuation, formatting, terminology, number conventions. A brand voice guide covers personality and tone: how the product sounds, emotional register variations, and "this not that" examples. You need both. The style guide prevents inconsistency. The voice guide prevents blandness.

Sentence case is the industry standard for product UI. Apple, Google, Microsoft, and most modern SaaS products use sentence case for headings, buttons, and menu items. Sentence case is easier to read, looks less formal, and avoids the ambiguity of title case rules (is "to" capitalized?). If your product already uses title case consistently, switching is a significant effort. For new products, start with sentence case.

Two sentences maximum. The first sentence states what happened. The second sentence tells the user what to do next. If the error requires more explanation, link to a help article. Long error messages are not read. Example: "Could not connect to the database. Check your credentials in Settings > Connections."

A content designer or content lead. In smaller teams, the product designer or PM who cares most about copy quality. The maintainer is responsible for keeping the terminology list current, resolving style disputes, and onboarding new writers. The guide should be stored where everyone can access it: in the design system docs, in a shared wiki, or in the component library.

Three approaches that work: (1) Provide a copy-paste library of standard UI strings (error messages, empty states, success messages) so engineers do not have to write copy from scratch. (2) Add a linter or CI check that catches common violations (banned words, incorrect capitalization patterns). (3) Include copy review in the PR process for any user-facing string changes. Make it easy and automated, not manual and burdensome.