Is "Which" Capitalized in a Title?

Yes. "Which" is a pronoun or determiner ("Which Style Guide Is Right?," "The Tool Which Saved Us"), and every style guide capitalizes it in a title.

"Which" by Style Guide

Style guide	"Which" mid-title	Why
AP	Capitalize	Pronouns are major words
APA	Capitalize	Pronouns are major words
Chicago	Capitalize	Pronouns are major words
MLA	Capitalize	Pronouns are major words
AMA	Capitalize	Pronouns are major words
Bluebook	Capitalize	Pronouns are major words

Examples in Chicago Style

• Which Style Guide Should You Use
• The Tools Which Saved Us Time
• Which Headline Wins
• Pick Which Rule to Follow

"Who", "what", and "that" are capitalized for the same reason.

For the short list of words that do stay lowercase, see the full list of words that stay lowercase.

"Which" in Sentence Case

APA reference lists, many news sites, and most UI text use sentence case instead of title case. There, only the first word and proper nouns get capitals, so "which" is lowercase unless it starts the title: "Which style guide should you use." Pick one of the two styles for a whole set of headings rather than mixing them.

Quick Answers

Should "which" be capitalized in a title?

Yes. "Which" is a pronoun, and every style guide capitalizes pronouns in title case.

Is "which" capitalized in APA?

Yes. APA capitalizes major words, including pronouns, regardless of length.