Title case is a capitalization system rather than one fixed algorithm. Most systems capitalize important words, but exact treatment varies among APA, Chicago, MLA, Microsoft, government, publisher, and house styles.
ReviewedEvidence2 sourcesSectionWriting & Style
Quick answer
Title case capitalizes selected words in titles and headings, but there is no single universal list of words to capitalize. Use the rules of the required style guide, especially for short conjunctions, articles, prepositions, hyphenated compounds, and words after punctuation.
Key details
Boundaryexact major/minor-word rules are style-specific
Common Principlemajor words are commonly capitalized while some function words may remain lower case
Core Issuestyle-governed capitalization of titles/headings
Important caveats
Boundary
Do not merge APA, Chicago, MLA, AP, Microsoft, or publisher-specific rules into one universal algorithm.
Further guidance
Contrast
Sentence case normally capitalizes the first word and independently capitalized terms, whereas title case capitalizes additional words according to a style system.
Decision Path
Identify the governing style before resolving edge cases; use the generic concept only when no named style applies.
Worked Example
A generic heading might appear as “Planning a Better Review,” but whether a short preposition is capitalized in another title depends on the required style.
Sources and evidence
Sources are shown with the role they play in this guide. Historical or style-sensitive claims are kept within the evidence boundary described above.
Capitalization checklist↗ (opens in a new tab)Microsoft Style Guide · Microsoft applies sentence-style capitalization broadly to headings, labels, titles, and phrases while preserving proper nouns and named products, showing the rule and its exceptions.
APA title case capitalizes the first word, the first word of a subtitle, major words, and words of four letters or more while keeping short minor words lowercase in ordinary mid-title positions.
Chicago 18 uses title case for titles of works and changed a long-standing rule: prepositions of five letters or more are now capitalized. Shorter prepositions generally remain lowercase internally, while first and last words are capitalized and “to” remains lowercase as an infinitive marker in ordinary mid-title use.
Hyphenated compounds cannot be capitalized safely with one universal “capitalize everything after a hyphen” rule. APA explicitly capitalizes the second part of hyphenated major words, while Chicago 18 changed its prefix-compound treatment and still applies grammatical title-case rules to individual elements.
MLA 9 describes title style as capitalizing the first word, last word, and all principal words. MLA’s public Style Center also documents the traditional lowercase treatment of internal prepositions, but its detailed preposition article is edition-labeled for MLA 8, so this engine does not yet treat the full MLA 9 converter profile as complete.
Multiword prepositions such as “according to,” “because of,” “instead of,” “out of,” and “up to” should not be handled by a single crude small-word list. Different style systems analyze components differently, and some phrases contain words that can change grammatical role.
Part of speech can change title capitalization for surface-identical words such as “than,” “like,” “over,” “off,” and phrasal particles. A reliable converter therefore needs reviewed grammatical context instead of a single lowercase-word list.
Short words such as “up,” “out,” and “on” can change capitalization when their grammatical role changes. Chicago’s own examples capitalize “Up” or “Out” when those words function adverbially in a phrasal verb, while ordinary prepositional uses can remain lowercase.
Prepositions are one of the clearest places where title styles diverge. APA uses a four-letter major-word threshold, Chicago 18 capitalizes prepositions of five letters or more, and MLA editorial guidance generally lowercases internal prepositions regardless of length.
