AP vs Chicago vs APA vs MLA: Title Case Rules Compared
Updated April 2026 · 10 min read
Four style guides, four sets of rules for capitalizing titles - and the differences between them aren't always obvious. If you've ever formatted a headline in AP style only to learn your professor wanted APA, or written a book title in Chicago style when your editor follows MLA, you know the frustration.
This guide puts all four major title case styles side by side so you can see exactly where they agree, where they differ, and which one to use for your situation. And if you'd rather skip the manual work entirely, our free headline capitalizer handles all four styles automatically.
In This Guide
The Four Styles at a Glance
Before we get into the details, here's a quick rundown of who uses each style and where it comes from:
AP Style
Source: Associated Press Stylebook
Used by: Newspapers, news websites, blogs, press releases, marketing copy. The most common style for online publishing.
Chicago Style
Source: Chicago Manual of Style (17th ed.)
Used by: Book publishers, magazines, literary journals, nonfiction authors. The standard for book publishing.
APA Style
Source: APA Publication Manual (7th ed.)
Used by: Psychology, social sciences, education, nursing. Required for most college research papers in these fields.
MLA Style
Source: MLA Handbook (9th ed.)
Used by: English, literature, languages, cultural studies. Standard for humanities papers and literary criticism.
Where All Four Styles Agree
Despite their differences, AP, Chicago, APA, and MLA all share the same foundational rules. These are the non-negotiables that every title case style follows:
- Capitalize the first word of the title, always, no exceptions.
- Capitalize the last word of the title (AP, Chicago, and MLA explicitly state this; APA follows the same convention).
- Capitalize all nouns, verbs, adjectives, adverbs, and pronouns - the "major" words.
- Capitalize short verbs like "is," "be," "are," "do," and "go" - these are always capitalized in every style because verbs are major words.
- Lowercase articles (a, an, the) when they appear in the middle of a title.
If your title only contains nouns, verbs, and articles, it'll look exactly the same in all four styles. The differences show up when you start dealing with prepositions, conjunctions, and special cases.
The Preposition Problem
Prepositions are where these four styles diverge the most. Words like "with," "from," "between," "through," and "into" get treated very differently depending on which guide you're following.
| Rule | AP | Chicago | APA | MLA |
|---|---|---|---|---|
| Short prepositions (in, of, to, at, by, on) | lowercase | lowercase | lowercase | lowercase |
| 4-letter prepositions (with, from, into, over) | Capitalize | lowercase | Capitalize | lowercase |
| Long prepositions (between, through, without) | Capitalize | lowercase | Capitalize | lowercase |
The key takeaway:
- AP and APA use a four-letter cutoff - capitalize any preposition with 4 or more letters.
- Chicago lowercases all prepositions regardless of length (except when they're the first or last word).
- MLA also lowercases all prepositions, similar to Chicago.
This is the single biggest difference between the styles. If you see "With" or "From" capitalized in a title, it's probably following AP or APA rules. If those same words are lowercase, it's likely Chicago or MLA.
Conjunctions and Articles
Coordinating conjunctions (and, but, or, nor, for, yet, so) and articles (a, an, the) are another area where styles diverge, though the differences are smaller than with prepositions.
| Word Type | AP | Chicago | APA | MLA |
|---|---|---|---|---|
| Articles (a, an, the) | lowercase | lowercase | lowercase | lowercase |
| Short conjunctions (and, but, or, nor) | lowercase | lowercase | lowercase | lowercase |
| "Yet" and "so" (3 letters) | lowercase | lowercase | lowercase | lowercase |
| Subordinating conjunctions (because, although, while) | Capitalize | Capitalize | Capitalize | Capitalize |
Good news: all four styles agree on conjunctions and articles for the most part. Coordinating conjunctions stay lowercase, and subordinating conjunctions are capitalized. The small wrinkle is that AP applies its four-letter rule here too - so "also" (a conjunctive adverb) would be capitalized across the board anyway since it's 4 letters and an adverb.
Hyphenated Words
Hyphenated compounds are where title case gets genuinely tricky, and every style handles them a little differently.
| Example | AP | Chicago | APA | MLA |
|---|---|---|---|---|
| well-known | Well-Known | Well-Known | Well-Known | Well-Known |
| self-esteem | Self-Esteem | Self-Esteem | Self-Esteem | Self-Esteem |
| e-book | E-Book | E-book | E-Book | E-Book |
| runner-up | Runner-Up | Runner-up | Runner-Up | Runner-Up |
The general patterns:
- AP, APA, and MLA tend to capitalize both elements of a hyphenated compound if each part is a major word or has 4+ letters.
- Chicago is the most conservative - it only capitalizes the second element if it's a major word (noun, verb, adjective, adverb). Prefixes like "e-" and small words like "up" in "runner-up" stay lowercase in Chicago.
This is one of the areas that regularly trips up writers switching between styles. When in doubt, run it through the capitalizer to see how each style handles your specific compound.
Words After Colons
What happens to the first word after a colon in a title? It depends on which style you're following.
| Style | Rule After Colon |
|---|---|
| AP | Capitalize if it begins a complete sentence; otherwise lowercase. |
| Chicago | Always capitalize the first word after a colon in a title. |
| APA | Always capitalize the first word after a colon, a dash, or end punctuation in a title. |
| MLA | Capitalize the first word after a colon if it begins an independent clause or is normally capitalized. |
In practice, here's how this plays out with a subtitle:
Example title: "Writing Well: a practical guide"
- AP: Writing Well: a Practical Guide (not a complete sentence, so "a" stays lowercase)
- Chicago: Writing Well: A Practical Guide (always capitalize after colon)
- APA: Writing Well: A Practical Guide (always capitalize after colon)
- MLA: Writing Well: A Practical Guide (capitalize if independent clause)
Same Headline, Four Ways
The fastest way to see the differences between styles is to run the same headline through all four. Here are five real-world examples showing where the styles produce different results:
Example 1: "how to deal with stress at work and at home"
AP: How to Deal With Stress at Work and at Home
Chicago: How to Deal with Stress at Work and at Home
APA: How to Deal With Stress at Work and at Home
MLA: How to Deal with Stress at Work and at Home
"With" (4 letters) is the key difference - capitalized in AP and APA, lowercase in Chicago and MLA.
Example 2: "the bridge between science and art"
AP: The Bridge Between Science and Art
Chicago: The Bridge between Science and Art
APA: The Bridge Between Science and Art
MLA: The Bridge between Science and Art
"Between" is a 7-letter preposition - capitalized in AP and APA, lowercase in Chicago and MLA.
Example 3: "a step-by-step guide to writing better headlines"
AP: A Step-by-Step Guide to Writing Better Headlines
Chicago: A Step-by-Step Guide to Writing Better Headlines
APA: A Step-by-Step Guide to Writing Better Headlines
MLA: A Step-by-Step Guide to Writing Better Headlines
All styles agree here - "Step" is a noun both times, so it's capitalized. Most styles lowercase "by" as a short preposition between hyphenated parts.
Example 4: "running from problems: why avoidance never works"
AP: Running From Problems: Why Avoidance Never Works
Chicago: Running from Problems: Why Avoidance Never Works
APA: Running From Problems: Why Avoidance Never Works
MLA: Running from Problems: Why Avoidance Never Works
Two differences: "From" (preposition, 4 letters) and the word after the colon. All styles capitalize "Why" here because it begins a complete sentence and is an adverb.
Example 5: "traveling through europe without a plan"
AP: Traveling Through Europe Without a Plan
Chicago: Traveling through Europe without a Plan
APA: Traveling Through Europe Without a Plan
MLA: Traveling through Europe without a Plan
Two long prepositions here. AP and APA capitalize both "Through" (7 letters) and "Without" (7 letters). Chicago and MLA lowercase them.
Want to see how your own headline looks in all four styles at once? Our tool has a Compare All Styles feature that shows all four side by side with the differences highlighted.
Which Style Should You Use?
The short answer: use whichever your publisher, professor, or organization requires. If nobody has told you which to follow, here's a practical guide:
Writing for the web, a blog, or marketing?
Use AP style. It's the most widely used for online content, and most readers are accustomed to seeing AP-formatted headlines without even realizing it.
Writing a book or long-form nonfiction?
Use Chicago style. Most book publishers follow CMOS, and it's the assumed default in publishing unless told otherwise.
Writing an academic paper in science or social science?
Use APA style. Required for psychology, education, nursing, and most social science journals. Note that APA uses title case for headings and reference titles but sentence case for article titles in reference lists.
Writing a literature or humanities paper?
Use MLA style. Standard for English, literature, cultural studies, and most humanities courses at the university level.
If you're writing for yourself and just want consistency, AP is the safest choice. It's the most familiar to general audiences and it's what most content platforms and CMS tools default to.
Quick Reference Table
Bookmark this table for a fast answer when you need to know the difference:
| Feature | AP | Chicago | APA | MLA |
|---|---|---|---|---|
| Preposition rule | 4+ letters cap | All lowercase | 4+ letters cap | All lowercase |
| Short verbs (is, be) | Capitalized | Capitalized | Capitalized | Capitalized |
| Articles (a, an, the) | lowercase | lowercase | lowercase | lowercase |
| After colon | If sentence | Always cap | Always cap | If indep. clause |
| Hyphenated words | Both parts if major | Conservative | Both parts if major | Both parts if major |
| First/last word | Always cap | Always cap | Always cap | Always cap |
| Primary use | Journalism | Publishing | Sciences | Humanities |
Compare All Four Styles Instantly
Type any headline and see it formatted in AP, Chicago, APA, and MLA side by side - with the differences highlighted.
Try the Capitalizer