Case converter

What each case looks like

The sentence “the quick brown fox jumps over the lazy dog” in every mode:

Title Case rules (Chicago Manual of Style)

Title Case follows The Chicago Manual of Style, 18th edition, published by the University of Chicago Press in 2024. Chicago’s rules, as the converter applies them:

• Capitalize the first and the last word of the title, and of a subtitle that follows a colon.
• Lowercase the articles a, an and the.
• Lowercase the conjunctions and, but, for, or and nor, and the words to and as.
• Lowercase prepositions of four letters or fewer. Since the 18th edition, prepositions of five or more letters are capitalized, so it is A Room with a View but Much Ado About Nothing, as the Chicago editors’ announcement explains.
• Capitalize every other word: nouns, pronouns, verbs, adjectives, adverbs, and words such as if, so and yet.

The words kept lowercase are: a, an, the, and, but, for, or, nor, to, as, at, by, down, from, in, into, of, off, on, onto, out, over, per, up, upon, via, with. Like, near and past are left out of the list because in titles they are more often a verb, an adjective or a noun (I Like It, The Past).

A few choices are the converter’s own, not Chicago’s. It cannot tell parts of speech apart, so a short preposition used as an adverb (Shut Up and Dance) comes out lowercase. Each part of a hyphenated word is treated as a word (Well-Known, Up-to-Date), while Chicago has finer rules for prefixes such as anti- and pre-. Name particles such as van or de are capitalized. Check those by hand. Each line is treated as a separate title.

Sentence case

The first letter of the text, of each line and of each sentence becomes a capital and everything else is lowercased. A sentence ends at a full stop, question mark, exclamation mark or ellipsis followed by a space, so “e.g. this” capitalizes “This”. The pronoun I is capitalized. Names of people and places are not, because the converter cannot know them.

The programming cases

camelCase, PascalCase, snake_case, kebab-case and CONSTANT_CASE first split the text into words at spaces, punctuation, underscores and hyphens, and at existing case changes, so XMLHttpRequest splits into XML, Http and Request and userAccountID becomes user_account_id. Numbers stay with the word before them. Apostrophes inside a word are dropped (don’t becomes dont). Accented letters are kept, so check that your programming language accepts them in names.

Unicode and long text

Letters are changed with the Unicode case rules built into your browser, so accents, Greek, Cyrillic and other scripts work. Greek capital sigma becomes ς at the end of a word and σ elsewhere. aLtErNaTiNg counts only letters that have a capital form, so spaces, numbers and emoji do not break the pattern. Each mode reads the text once from start to end, so a whole book of about 1 MB converts in well under a second.