Title case vs sentence case: which words get capitals

Two conventions, one question

The question every heading raises is which words get a capital letter. Sentence case answers: the ones grammar already capitalises — the first word and proper nouns. "How the budget was approved". Title case answers: the important ones — "How the Budget Was Approved".

Neither is more correct. Title case is the older publishing convention and still dominates American book and magazine titles; sentence case has steadily taken over the web, where most major products and publications now use it for everything, headlines included.

Sentence case: capitals as grammar

The rule fits in one line: capitalise exactly what a sentence would. First word, proper nouns, acronyms — nothing else.

Its appeal is operational as much as aesthetic. There are no judgement calls, so a team of ten writers produces consistent headings without consulting a style sheet, and nobody has to decide whether "with" is an important word today. It also reads calmer, which is why interface text has moved almost entirely to sentence case: buttons and menus full of Capitalised Words read as shouting at small sizes.

Title case: capitals by style sheet

Title case capitalises "major" words — and the styles disagree about which words those are, which is why two carefully edited publications can title the same article differently.

• All styles agree: capitalise the first and last word, and all nouns, pronouns, verbs, adjectives, and adverbs.
• All styles agree: lowercase the articles a, an, and the (unless first or last).
• AP style capitalises prepositions and conjunctions of four letters or more — With, Over, Because.
• Chicago style lowercases prepositions regardless of length — with, over, between — but capitalises subordinating conjunctions like Because.

So "Working With Data Between Releases" is AP, and "Working with Data between Releases" is Chicago, and both are right by their own book. If a house style exists, it settles the argument; if not, picking either and staying consistent matters more than the pick.

The words people trip over

A few cases catch even careful writers:

• Short verbs are always capitalised: Is, Be, Go. Length is not the test — word class is. "It" and "Its" get capitals too.
• Particles in phrasal verbs count as part of the verb: "Set Up Your Account", not "Set up". The same word as a plain preposition stays lowercase in Chicago: "Walking up the Hill".
• Hyphenated compounds: major styles capitalise both parts of an ordinary compound — "Follow-Up Questions" — but not a prefix half like "Re-elect".
• Acronyms and proper-noun casing survive either convention: NASA stays NASA, iPhone keeps its lowercase i, in title case and sentence case alike.

What a mechanical converter can and cannot do

A case-conversion tool applies mechanical rules, and it is worth knowing exactly which. Simple title case — what most tools and headline fields produce — capitalises every word, including the ones AP and Chicago would lowercase. That matches many CMS expectations, but if your house style lowercases minor words, a handful need lowering by hand afterwards.

Mechanical sentence case has the opposite blind spot: it lowercases everything first and then recapitalises sentence starts, so it cannot know that "nasa" was an acronym or "smith" a surname. The conversion gets the shape right in one click; proper nouns need the human pass.

This is not a limitation better software would remove — deciding that a word is a proper noun requires knowing the world, not the string. Convert mechanically, then proofread the names.