Title Case Rules: AP Style vs Chicago Style

Title case means capitalizing the first letter of major words in a heading. The two dominant style guides — AP (Associated Press) and Chicago — have different rules for which words to capitalize.

AP Style (used by journalists and news organizations): Capitalize the first and last words, all nouns, pronouns, adjectives, verbs, adverbs, and subordinate conjunctions (because, although). Lowercase articles (a, an, the), coordinating conjunctions (and, but, or), and prepositions regardless of length. Example: "How to Write Better Headlines for the Web."

Chicago Style (used by book publishers and academic presses): Capitalize the first and last words, all nouns, pronouns, verbs, adjectives, and adverbs. Lowercase articles, coordinating conjunctions, and prepositions — unless the preposition is five or more letters long. Under Chicago, prepositions like "through," "between," and "without" are capitalized. Example: "A Journey Through the History of Science."

Key difference: Preposition length. AP lowercases all prepositions. Chicago capitalizes prepositions of five or more letters. This is the most common point of divergence between the two styles.

When to use which: Follow the style guide specified by your publisher, institution, or organization. If no guide is specified, AP style is the safer default for online content and journalism. Chicago style is standard for academic and book publishing.

Tooler's Case Converter capitalizes every word in Title Case mode. For AP or Chicago compliance, manually review and lowercase articles, short prepositions, and conjunctions as appropriate.