AP Style vs Chicago Style Capitalization: Key Differences
The Associated Press Stylebook and The Chicago Manual of Style are the two most widely used style guides in American English. They agree on more than they disagree on, but their capitalization rules diverge in several ways that matter to anyone writing headlines, book titles, or formal copy. Understanding the differences will save you from second-guessing every preposition.
Who Uses Each Style?
AP Style is the default for journalism. Newspapers, news websites, press releases, broadcast scripts, and most corporate communications follow AP. The AP Stylebook is updated annually and emphasizes brevity, clarity, and speed of reading.
Chicago Style dominates book publishing, academic press, and long-form magazine work. The Chicago Manual of Style is more comprehensive — over a thousand pages — and treats English as a formal written language to be polished rather than scanned. If you are writing a novel, a textbook, a dissertation, or a piece for The Atlantic, Chicago is probably the house style.
The Big Difference: Preposition Length
The single most important difference is the length threshold for capitalizing prepositions in titles. AP capitalizes prepositions of four letters or more. Chicago capitalizes prepositions of five letters or more. That one-letter gap changes the look of many titles.
"With," "From," "Over" — all four letters:
AP: "Gone With the Wind"
Chicago: "Gone with the Wind"
"Between" — seven letters, both capitalize:
AP: "The Space Between Us"
Chicago: "The Space Between Us"
Side-by-Side Rule Comparison
| Rule | AP Style | Chicago Style |
|---|---|---|
| Prepositions capitalized at | 4+ letters | 5+ letters |
| "To" in infinitives | Lowercase | Lowercase |
| "As" | Lowercase | Lowercase |
| Hyphenated compounds | Capitalize both parts | Capitalize per part-of-speech |
| Headlines (news) | Sentence case allowed | Title case standard |
| Job title before name | Capitalize formal titles | Capitalize formal titles |
| Job title after name | Lowercase | Lowercase |
| Seasons | Lowercase (spring) | Lowercase (spring) |
| Internet, Web | Lowercase since 2016 | Lowercase since 2017 |
Hyphenated Compounds in Titles
AP Style is straightforward: capitalize both parts of a hyphenated compound in a title. "Self-Help," "Twenty-First," "Mother-In-Law." Chicago is more nuanced. It capitalizes parts that would be capitalized on their own and lowercases articles, prepositions, and coordinating conjunctions within the compound.
Hyphenated compound differences:
AP: "A How-To Guide to Cooking"
Chicago: "A How-to Guide to Cooking"
AP: "Mother-In-Law's Recipe Book"
Chicago: "Mother-in-Law's Recipe Book" (the "in" is a preposition under three letters)
Both: "Twenty-First-Century Writing" — "Twenty," "First," and "Century" are all major words.
Headline Style: Sentence Case Gains Ground
AP traditionally used "down-style" headlines — sentence case with only the first word and proper nouns capitalized — for news headlines. Many wire-service papers still follow this. Chicago does not have an opinion on news headlines specifically, but for book and chapter titles, it always uses title case.
Web-first publishers have blurred the line. Many AP-trained newsrooms now use title case online for SEO reasons (headlines look more authoritative in search results) while keeping sentence case in print. See our breakdown of sentence case vs title case for the full discussion.
Job Titles: Both Agree (Mostly)
Both AP and Chicago capitalize a formal job title only when it directly precedes a person's name without intervening punctuation. After the name, or used generically, the title is lowercase.
Job title examples (same for AP and Chicago):
✅ "President Joe Biden announced the policy."
✅ "Joe Biden, the president, announced the policy."
✅ "The president announced the policy."
❌ "The President announced the policy." (generic — should be lowercase)
The exceptions: titles of nobility (the Queen, the Pope) and certain religious figures may be capitalized as a sign of respect in both styles, though AP has moved away from this in recent editions.
Geographic and Directional Terms
Both styles agree that compass directions are lowercase (drive south for two miles) but regions are capitalized when they refer to a defined cultural area (the South, the Midwest, the Pacific Northwest). Chicago is slightly more permissive about capitalizing region names; AP requires the region to be widely recognized.
Which Should You Pick?
Pick the guide your industry expects. Journalists, PR pros, and marketers default to AP. Book authors, scholars, and editors default to Chicago. Tech companies often write their own internal style guide that borrows from both (Microsoft, Google, and Apple all publish theirs). The worst choice is to mix the two in the same document.
Frequently Asked Questions
Is "with" capitalized in AP Style?
Yes. "With" is four letters, which meets AP's threshold. Chicago, which uses a five-letter threshold, keeps it lowercase.
Does AP Style use title case or sentence case for headlines?
Both are acceptable in AP. Many newspapers use sentence case for print headlines and title case online. The AP Stylebook itself recommends sentence case for news headlines.
What about MLA and APA?
MLA capitalizes every preposition regardless of length. APA agrees with AP on the four-letter threshold. See our APA title case rules guide for full APA details.