Title Case Rules by Style Guide

Rules the converter applies

• The first word is capitalized.
• A phrase break is a colon. The first word after one is capitalized.
• The last word, and the last word before a phrase break, is capitalized, even a short word from the list.
• Both parts of a two-part hyphenated compound are capitalized. In longer compounds, words from the list stay lowercase.

Words kept lowercase (22)

Unless a rule above capitalizes them: a, an, the, and, as, but, for, if, nor, or, so, yet, at, by, in, of, off, on, per, to, up, via. Every other word is capitalized.

Sources

• AP Stylebook (the composition titles entry needs a subscription) (The Associated Press)

Where the sources leave room

• The AP site needs a subscription, so the entry was read through a published summary of it.
• Treating subordinating conjunctions such as "if" as conjunctions, and capitalizing both parts of a two-part compound (Follow-Up, All-In), come from AP "Ask the Editors" answers as reported by a third-party site, not read on the AP site itself.
• The entry does not cover subtitles. The converter capitalizes the word after a colon and the word before it, as it does in Chicago and MLA style.
• AP gives no rule for compounds of three or more parts, so short words inside them stay lowercase (Mother-in-Law), as in Chicago, APA, and MLA.

Known limits

• Only a colon starts a subtitle. After a question mark or exclamation point, the next word follows the normal rules, so a short word stays lowercase.

Test cases (14)

Rules the converter applies

• The first word is capitalized.
• A phrase break is a colon. The first word after one is capitalized.
• The last word, and the last word before a phrase break, is capitalized, even a short word from the list.
• In a hyphenated compound, the first part is capitalized and later parts are capitalized unless they are on the list.

Words kept lowercase (29)

Unless a rule above capitalizes them: a, an, the, and, but, for, nor, or, as, amid, at, atop, by, from, in, into, of, off, on, onto, over, per, till, to, unto, up, upon, via, with. Every other word is capitalized.

Sources

• CMOS Online Q&A: Capitalization, Titles (The University of Chicago Press)
• The Chicago Manual of Style Online (The University of Chicago Press)

Where the sources leave room

• Capitalizing "that" is an inference from 8.160, which lowercases only the conjunctions and, but, for, or, and nor. The sources give no example with "that".

Known limits

• Chicago lowercases a preposition only when it works as one. The converter always lowercases the short prepositions in its list, such as "over" and "up", even as adverbs, and always capitalizes words it leaves off the list because they are usually other parts of speech in titles: down, like, near, out, past, and than.
• Only a colon starts a subtitle. After a question mark or exclamation point, the next word follows the normal rules, so a short word stays lowercase.

Test cases (15)

Rules the converter applies

• The first word is capitalized.
• A phrase break is a colon, an em dash, a horizontal bar, a period, a question mark, and an exclamation point. The first word after one is capitalized.
• The last word has no exception: a short word from the list stays lowercase at the end.
• In a hyphenated compound, the first part is capitalized and later parts are capitalized unless they are on the list.

Words kept lowercase (22)

Unless a rule above capitalizes them: a, an, the, and, as, but, for, if, nor, or, so, yet, at, by, in, of, off, on, per, to, up, via. Every other word is capitalized.

Sources

• APA Style: Title Case Capitalization (American Psychological Association)

Where the sources leave room

• The APA page lists no exception for the last word, so a short minor word at the end of a title stays lowercase (What Are You Looking at). The converter follows the page; the other styles capitalize the last word.
• Minor words inside a compound of three or more parts stay lowercase (All-or-None). This follows the minor-word rule; the page shows no such example.

Known limits

• APA capitalizes every word of four or more letters, so only the short words in the list depend on part of speech. Those are always lowercased.

Test cases (15)

Rules the converter applies

• The first word is capitalized.
• A phrase break is a colon, a question mark, and an exclamation point. The first word after one is capitalized.
• The last word, and the last word before a phrase break, is capitalized, even a short word from the list.
• In a hyphenated compound, the first part is capitalized and later parts are capitalized unless they are on the list.
• A lowercase abbreviation such as etc. is capitalized when it is the last word.

Words kept lowercase (64)

Unless a rule above capitalizes them: a, an, the, and, but, for, nor, or, so, yet, according, concerning, regarding, about, above, across, after, against, along, amid, among, around, as, at, atop, before, behind, below, beneath, beside, between, beyond, by, despite, during, except, from, in, inside, into, near, of, off, on, onto, outside, over, per, through, throughout, till, to, toward, towards, under, underneath, unlike, unto, up, upon, via, with, within, without. Every other word is capitalized.

Sources

• MLA Style Center: Two-word prepositions in titles (Modern Language Association)
• MLA Style Center: Capitalizing "etc." in a title (Modern Language Association)
• MLA Style Center: Articles at the start of subtitles (Modern Language Association)

Where the sources leave room

• The Style Center posts were written for the 8th edition. A library guide to the 9th edition states the same rules.
• The rule that a question mark or exclamation point can end the main title without a colon (9th edition, p. 61) was read in a school library guide that quotes the handbook, not in the handbook itself.
• The converter treats every question mark and exclamation point in a line as the end of a main title, even one inside it.

Known limits

• MLA lowercases prepositions by part of speech. The converter always capitalizes down, like, out, past, since, and until, which are often other parts of speech in titles, and always lowercases after, before, and as, even when they start a clause as subordinating conjunctions, which MLA capitalizes.

Test cases (16)