AP vs. Chicago vs. APA Title Case Rules (With Examples)

If you've ever had a title come back from your editor with "Over" lowercased and then had the next editor capitalize it, you've already met the chaos of title case rules. The three most-used style guides in US English — AP Stylebook (Associated Press), Chicago Manual of Style (CMOS), and APA Publication Manual — agree on the broad strokes of title case and disagree on a handful of small, maddening details.

This article lays out the actual rules of each guide, gives you the small-words lists, walks through worked examples, and ends with a cheat sheet you can keep on your desk (or in a browser bookmark). It's the reference I wish I'd had when I was getting started.

The shared foundation

Before we get to the disagreements, the things all three guides agree on. Under all three style guides, in title case you:

Always capitalize the first word of a title, subtitle, or heading — even if it's a word that would normally be lowercase.
Always capitalize the last word — same reason.
Always capitalize verbs — including forms of "to be" (is, are, was, be, been, being) and helping verbs (has, have, had, do, does, did, can, could, will, would, shall, should, may, might, must). This is where beginners slip most often, because "is" and "are" don't feel like words that should be capitalized.
Always capitalize all words of four letters or more — except where a guide specifically says otherwise (Chicago does say otherwise for prepositions).
Capitalize both parts of a hyphenated compound if both parts are principal words (e.g., "State-of-the-Art," "Self-Sufficient," "Long-Term").
Lowercase articles: a, an, the.
Lowercase coordinating conjunctions: and, but, or, for, nor (and in some guides, yet, so).

That's the common core. Everything beyond this is where the guides diverge.

AP Stylebook

AP Style is the lingua franca of US journalism. If you're writing for a newspaper, a wire service, or most corporate PR, AP is what you'll be held to. The current edition is the AP Stylebook, 57th edition (2024).

The rule

AP capitalizes the principal words and lowercases articles, coordinating conjunctions, and prepositions of three letters or fewer. Prepositions of four or more letters are capitalized.

What to lowercase

Articles: a, an, the
Coordinating conjunctions: and, but, or, for, nor, so, yet
Prepositions of three letters or fewer: as, at, by, for, in, of, on, to, up, via, but (yes, "but" appears in both lists — when it's a conjunction it's lowercase, when it's a preposition it's lowercase too; AP doesn't distinguish)

What to capitalize

Everything else, including prepositions of four letters or more: From, Into, With, Over, Upon, About, Above, After, Along, Around, Before, Below, During, Through, Under, Until, Within, Without

AP example walkthroughs

The Quick Brown Fox Jumps Over the Lazy Dog — "the" before "Lazy" is an article (lowercase); "Over" is four letters (capitalized); "the" before "Lazy" is an article (lowercase).
From Here to Eternity — "From" is four letters (capitalized); "to" is two letters (lowercase).
How to Be a Better Writer in 30 Days — "to" lowercase (preposition, two letters); "Be" capitalized (verb); "a" lowercase (article); "in" lowercase (preposition, two letters).
A Walk in the Park — "A" first word (capitalized); "in" preposition two letters (lowercase); "the" article (lowercase).
Bringing Out the Best in People — "Out" is an adverb, capitalized. "the" article, lowercase. "in" preposition two letters, lowercase.
With Liberty and Justice for All — "With" preposition four letters (capitalized); "and" coordinating conjunction (lowercase); "for" preposition three letters (lowercase).

AP-specific quirks

"Than" is treated as a conjunction and lowercased. "More Than Meets the Eye" — "than" lowercase.
"As" is treated as a preposition/conjunction and lowercased. "As Good as It Gets" — both "as" instances lowercase.
"To" in infinitives is lowercase. "To Kill a Mockingbird" — "to" lowercase.
"Up" is three letters, lowercase. "Up in the Air" — "up" lowercase (when used as a preposition; if it's an adverb, as in "Looking Up," it's capitalized). This is the kind of judgment call that drives writers crazy.

Chicago Manual of Style

Chicago is the standard for book publishing, academic writing in the humanities, and any writer who needs to cite sources in footnotes. The current edition is the Chicago Manual of Style, 17th edition (2017; 18th edition released September 2024 with mostly minor title case changes).

The rule

Chicago capitalizes the first and last words and all nouns, pronouns, adjectives, verbs, adverbs, and subordinating conjunctions. It lowercases articles, coordinating conjunctions, and all prepositions, regardless of length.

This is the big difference from AP and APA: Chicago lowercases "With," "From," "Into," "Without," "Through," "Between," and every other preposition, no matter how long. Many writers find this looks wrong on the page, which is why Chicago-style titles often look subtly different from AP-style titles.

What to lowercase

Articles: a, an, the
Coordinating conjunctions: and, but, or, for, nor, so, yet (Chicago recognizes seven)
All prepositions, regardless of length: of, in, to, for, with, on, at, from, by, about, as, into, like, through, after, over, between, out, against, during, without, before, under, around, among, behind, beyond, including, concerning, etc.

What to capitalize

Nouns, pronouns, adjectives, verbs (including forms of "to be"), adverbs, subordinating conjunctions (because, although, while, if, unless, since, when, where, etc.)
"Not" — capitalized as an adverb
"Why," "How," "Where," "When" — capitalized as adverbs

Chicago example walkthroughs

The Quick Brown Fox Jumps over the Lazy Dog — "over" is a preposition, lowercase (this is the visible Chicago-vs-AP difference)
From Here to Eternity — "From" is a preposition, lowercase: from Here to Eternity — wait, no. "From" is the first word, so it's capitalized regardless: From Here to Eternity. "to" preposition, lowercase.
How to Be a Better Writer in Thirty Days — "to" preposition, lowercase; "Be" verb, capitalized; "a" article, lowercase; "in" preposition, lowercase.
A Walk in the Park — same as AP.
Bringing Out the Best in People — "Out" is an adverb, capitalized. "in" preposition, lowercase.
With Liberty and Justice for All — "With" is a preposition; it's also the first word, so capitalized. "and" coordinating conjunction, lowercase. "for" preposition, lowercase.
The Lord of the Rings: The Fellowship of the Ring — "of" and "the" lowercase (preposition and article). Note that under Chicago, the subtitle's first word ("The") is capitalized because it's the first word of a subtitle.

Chicago-specific quirks

Hyphenated compounds. Chicago capitalizes both parts if they're principal words: "State-of-the-Art," "Long-Term," "Self-Sufficient." But it lowercases the second part if it's an article, preposition, or coordinating conjunction: "Mother-in-Law" (the "in" stays lowercase), "Editor-in-Chief" (the "in" stays lowercase). Note that "in-law" sometimes appears as "In-Law" in the middle of a title — Chicago style would lowercase it.
Prefixes. Chicago lowercases prefixes like "anti," "pre," "re," "un" before a capitalized word in some contexts: "anti-American," "pre-Columbian." But in titles, you generally capitalize the prefix because it's part of a compound: "Anti-Intellectualism in American Life."
"Versus" and "vs." Chicago treats "versus" as a preposition, lowercase. "Revenge versus Justice" — "versus" lowercase.
"To" in infinitives. Lowercase, same as AP.
Subordinating conjunctions. Chicago capitalizes "Because," "Although," "While," "If," "Unless," "Since," "When," "Where," "Whether" — these are subordinating conjunctions, not prepositions, and Chicago treats them as principal words. AP and APA often lowercase these.

APA Publication Manual

APA Style governs academic writing in psychology, education, the social sciences, and most nursing and allied health fields. The current edition is the Publication Manual of the APA, 7th edition (2019).

The rule

APA capitalizes the first word of the title, the first word of a subtitle (the word immediately following a colon, em dash, or end punctuation within the title), all principal words, and any word of four letters or more. It lowercases articles, coordinating conjunctions, and prepositions of three letters or fewer.

APA is, in practice, almost identical to AP for title case. The differences from AP are minor and mostly involve edge cases around the treatment of certain words.

What to lowercase

Articles: a, an, the
Coordinating conjunctions: and, but, or, for, nor, so, yet (APA includes "so" and "yet" in the lowercase list explicitly)
Prepositions of three letters or fewer: as, at, by, for, in, of, on, to, up (APA's example list)

What to capitalize

All words of four letters or more, including prepositions: With, From, Into, Over, About, After, Along, Around, Before, Below, During, Through, Under, Until, Within, Without, Between, Against, Beyond
All verbs, including forms of "to be" (a common APA-specific error is lowercasing "is" or "are")
All nouns, pronouns, adjectives, adverbs

APA example walkthroughs

The Quick Brown Fox Jumps Over the Lazy Dog — same as AP.
From Here to Eternity — same as AP. "From" four letters, capitalized.
How to Be a Better Writer in 30 Days — same as AP.
With Liberty and Justice for All — same as AP.
Bringing Out the Best in People — same as AP.

APA-specific quirks

Subtitles. APA is unusually explicit that the first word after a colon, em dash, or sentence-ending punctuation in a title is always capitalized, even if it would normally be lowercase. Title of Work: A Subtitle — "A" is capitalized because it follows a colon.
"That." APA capitalizes "that" because it's a subordinating conjunction (and four letters). The Idea That Changed Everything — "That" capitalized. AP also capitalizes it (four letters); Chicago capitalizes it (subordinating conjunction).
"Than." APA lowercases "than" as a conjunction. "More Than Meets the Eye" — "Than" is four letters, so capitalized under APA's length rule. This is one of the rare cases where the "length rule" overrides the conjunction rule.
Hyphenated compounds. APA capitalizes both elements of a hyphenated compound if they're major words, lowercases the second if it's an article/preposition/conjunction. Same as Chicago in practice.

Side-by-side comparison

To make the differences concrete, here are ten titles rendered in each of the three styles. Look for the small but visible differences — usually a single word here or there.

| Title (in plain text) | AP | Chicago | APA |

|---|---|---|---|

| The quick brown fox jumps over the lazy dog | The Quick Brown Fox Jumps Over the Lazy Dog | The Quick Brown Fox Jumps over the Lazy Dog | The Quick Brown Fox Jumps Over the Lazy Dog |

| The lord of the rings: The fellowship of the ring | The Lord of the Rings: The Fellowship of the Ring | The Lord of the Rings: The Fellowship of the Ring | The Lord of the Rings: The Fellowship of the Ring |

| Why we sleep: Unlocking the power of sleep and dreams | Why We Sleep: Unlocking the Power of Sleep and Dreams | Why We Sleep: Unlocking the Power of Sleep and Dreams | Why We Sleep: Unlocking the Power of Sleep and Dreams |

Notice the differences cluster around the same handful of words: over, versus, and longer prepositions. In most everyday titles, the three guides produce identical results, which is part of why people are surprised when they don't.

The small-words cheat sheet

Here's a printable quick reference: a single list of words that are lowercased in at least one of the three major style guides, with notes on which guide does what.

ARTICLES (lowercase in all three):
  a, an, the

COORDINATING CONJUNCTIONS (lowercase in all three):
  and, but, or, for, nor
  (Chicago, APA also lowercase: so, yet — AP varies)

PREPOSITIONS, TWO LETTERS (lowercase in all three):
  at, by, in, of, on, to, up, as

PREPOSITIONS, THREE LETTERS (lowercase in all three):
  for (also a conjunction), out (when prep)

PREPOSITIONS, FOUR LETTERS (the divergence):
  from, into, with, over, upon, past, like, than (when conj)
  → AP: capitalize
  → APA: capitalize (4+ letter rule)
  → Chicago: lowercase (all prepositions lowercase)

PREPOSITIONS, FIVE+ LETTERS:
  about, above, after, along, among, around, before, behind,
  below, beneath, beside, between, beyond, during, except,
  inside, into, near, outside, over, since, through, toward,
  towards, under, underneath, until, upon, within, without,
  versus
  → AP: capitalize
  → APA: capitalize
  → Chicago: lowercase

SUBORDINATING CONJUNCTIONS:
  although, because, if, since, unless, when, whenever,
  where, whereas, whether, while
  → All three: capitalize (these are principal words)

VERBS (always capitalize in all three):
  is, are, was, were, be, been, being, am, do, does, did,
  has, have, had, can, could, will, would, shall, should,
  may, might, must, go, see, make, take, get, etc.

If you want to test your eye: take the title "What to Do When Everything Goes Wrong" and apply each style. The result is identical under all three — "to" is a preposition two letters (lowercase), "Do" and "Goes" are verbs (capitalized), "When" is a subordinating conjunction (capitalized). The three guides agree far more than they disagree.

Hyphenated words: the special case

Hyphenated compounds cause more title-case errors than any other category. Here's how each guide handles them:

AP: Capitalize both parts of a hyphenated compound if both are equal: "State-of-the-Art." Lowercase the second part if it's an article, coordinating conjunction, or short preposition: "Mother-in-Law," "Editor-in-Chief." In practice, AP editors are inconsistent here; the safest rule is to capitalize both parts of equal compounds and lowercase articles/short prepositions in compounds.

Chicago: Same general rule as AP. "Self-Sufficient," "Long-Term," "Mother-in-Law" (in stays lowercase because it's a preposition). Chicago is the most explicit about this.

APA: Same as Chicago in practice.

A reasonable rule of thumb across all three: if both halves of the hyphenated compound are nouns, adjectives, or verbs, capitalize both. If the second half is an article, coordinating conjunction, or short preposition, lowercase it.

What about MLA and Microsoft?

Two other style guides come up often. MLA (Modern Language Association, used in literature and humanities) is very close to Chicago: lowercases all prepositions regardless of length, capitalizes principal words and subordinating conjunctions. The MLA Handbook, 9th edition is current. Microsoft / Apple style (product documentation) uses a 4-letter cutoff like AP and APA, with a few quirks. Microsoft's Style Guide is public. For everyday writing, treat MLA as "same as Chicago" and Microsoft as "same as AP."

Practical advice: which guide should you use?

Journalism, PR, corporate communications, news: AP. It's what your editor will hold you to.
Books, academic humanities, long-form nonfiction: Chicago.
Academic social sciences, psychology, education, nursing: APA.
Academic literature, language, cultural studies: MLA (≈ Chicago).
Software documentation: Microsoft style.
General web writing with no guide: Pick one. AP is the easiest to apply mechanically because its rules are length-based (lowercase prepositions of 3 letters or fewer; capitalize 4+).

Tools that get it right

Most "title case" tools online apply a simplified single-rule set: lowercase a, an, the, and, but, or, for, nor, on, in, at, to, by, of, up; capitalize everything else. This works ~80% of the time but fails the moment you hit "With" (capitalized in AP/APA, lowercased in Chicago) or "Is" (always a verb, always capitalized).

A good tool will let you pick a style guide. The TextKit title case converter handles AP, Chicago, and APA separately, applies the correct hyphenation rules, and always capitalizes forms of "to be." If you do this weekly, a style-guide-aware tool saves hours of manual correction.

The bottom line

The three major US style guides agree on title case ~85% of the time. The 15% where they disagree is concentrated in:

Prepositions of four or more letters (Chicago lowercases, AP/APA capitalize)
"Versus" and similar long prepositions (Chicago lowercase, AP/APA capitalize)
Subordinating conjunctions (all three capitalize, but Chicago is the most explicit)
The treatment of "so" and "yet" (some guides lowercase, some don't)

If you're writing for a publication, the publication's house style wins. If you're writing for yourself, pick one guide, learn its small-words list, and apply it consistently. The worst sin isn't picking the "wrong" guide — it's applying two guides' rules in the same document, which is what most writers do without realizing it.

For the broader question of when to use title case at all — versus sentence case — see our title case vs. sentence case comparison.