Sentence case vs title case

What each one is, which style guide asks for which, and the AP, APA and Chicago rules laid out side by side. Plus what happens when you let an app do it for you.

The short answer

Sentence case capitalises the first word and nothing else. Title case capitalises the important words and leaves the small ones down. Sentence case is the default for interface text, headings on the web and most British publishing. Title case is the default for American news headlines, book titles and academic reference lists.

Why nearly every design system picked sentence case

Two good reasons and one less dignified one. None of them is fashion: capitals carry information, and title case spends that information on words that do not need it.

• It scans faster. A reader recognises a word partly by its shape, and a capital at the front of every word flattens those shapes toward each other. The effect is small in a six-word headline and real in a menu of forty items, which is why interface text moved first and body headings followed.
• It keeps proper nouns visible. In "A Walk Between Worlds With Apple", the one word that is genuinely a name looks exactly like the four that are not. Sentence case leaves the capital meaning something.
• Title case is hard. Getting it wrong looks worse than not using it, and the rest of this page is about how often it goes wrong.

The three title case styles, and where they disagree

There is no single title case. There are several published ones, and the three that come up in ordinary work are AP, APA and Chicago. They agree about most of it and disagree about exactly two things.

The practical upshot is that you can spot the style from one sentence. Give all three a walk between worlds: a study of what works and they answer differently.

• AP: A Walk Between Worlds: a Study of What Works
• APA: A Walk Between Worlds: A Study of What Works
• Chicago: A Walk between Worlds: A Study of What Works

Pick one and hold it. A publication that mixes them looks less careful than one that picked the "wrong" style and stayed with it, because a reader notices inconsistency long before they notice a preposition.

What the tools actually do, measured

Every converter on page one claims to do title case and sentence case. They do not agree, and three of them break the text in ways their landing pages do not mention. So I pasted the same two sentences into each one by hand and wrote down exactly what came back.

Method. On 29 August 2026, in Chrome 151.0.7922.175 on macOS 26.6.2, I opened every converter ranking on the first page of Google for "case converter" in the United States, typed each test string into its own input, and pressed its own buttons. Nothing was retyped, nothing was cleaned up first, and every tool ran on its default settings. Two of the seven have no title case button at all, so the table names the button actually pressed.

Test one: the five things that are easy to get wrong

the NASA report on iPhone sales isn't a must-read for O'Brien. dr. smith agreed.

An acronym, a brand name with an inner capital, an apostrophe inside a word, a hyphenated compound, and an abbreviation that looks like the end of a sentence. In AP style the answer is The NASA Report on iPhone Sales Isn't a Must-Read for O'Brien.

Four failures worth naming, because each one tells you something about the tool that made it.

• The acronym is the tell. Four of the seven give Nasa and Iphone. Any tool that does is running a naive capitalise-the-first-letter pass, and it will flatten every brand name and every surname with an inner capital, which is why the same four also give O'brien.
• textmagic gives Isn'T. It treats the apostrophe as a word boundary, so the t starts a new word and gets a capital. It is the only one of the seven to do this, and it does it to every contraction you paste.
• convertcase.net gives Must-read. Its title case is otherwise the best of the non-specialists, but it does not capitalise after a hyphen. AP, APA and Chicago all want Must-Read.
• appdevtools deletes the punctuation. Both full stops, the apostrophe and the hyphen are gone, and iPhone has become two words. It is a tool for building identifiers, and building an identifier means throwing exactly those characters away.

Test two: does it know an abbreviation from a full stop?

we met at 4 p.m. and left early. it rained.

This one has a single correct answer and no room to argue: We met at 4 p.m. and left early. It rained. The stop after p.m. does not end a sentence, so and stays lowercase, and the m stays lowercase too.

Three tools produce the identical wrong answer, p.M. And, which means all three are splitting on "full stop followed by a space" with no list of abbreviations behind it. That is the single most common defect in this category and it fires on Dr., etc., e.g., vs., on initials, and on every date and time abbreviation.

It also explains something in the first test. All three gave Dr. Smith Agreed, which looks correct, and it is not: they capitalised Smith because they thought dr. had ended a sentence. Right answer, wrong reason, and the reason is what breaks on the next paragraph you paste.

Where floi comes off worse

On test two, floi and titlecaseconverter.com give the same output. On test one they also agree. But run the first test through sentence case rather than title case and they part company, and floi is the one that loses.

Smith against smith. titlecaseconverter.com carries a proper-noun dictionary, which its own option calls "Sentence Case (with proper noun recognition)", and floi does not. Nothing in the string says smith is a surname, so floi leaves it alone rather than guessing, and on this sentence the guess would have been right.

That tool also carries eight named title case styles to floi's three, and it can show you why it made each decision. If a style guide is the whole of your problem, it is the better page and this one will not pretend otherwise. What it does not do is camelCase, snake_case or any of the other identifier formats, and it needs a button press where the converter here updates as you type.

How to change case without a browser tool

Every app people write in has some version of this built in, and all of them are more limited than they look. The shortcut matters more than the menu, so here it is first. This table is a map of where the feature lives, not a second set of measurements: the numbers above came from tools I ran, and Word, Excel and Pages are not installed on the machine I ran them on.

Shift + F3 is a three-state cycle, not four

It steps through lower case, Capitalise Each Word and UPPER CASE, then returns to the first. Sentence case and tOGGLE cASE are in the Aa menu but not in the cycle, which is the reason people press the shortcut a fourth time expecting something new.

On a Mac laptop the function row is media keys by default, so the press is usually Fn + Shift + F3. On a full keyboard it is Shift + F3 as written.

A menu called Title Case is almost never title case

The one I could check line by line is VS Code, because it ships its source in the application bundle. Its Transform to Title Case command, read in version 1.135.0, lowercases the whole selection and then uppercases the first letter after every character that is not a letter, digit or apostrophe.

That is start case. It has no list of small words in it, so the lord of the rings becomes The Lord Of The Rings, which is not AP, APA or Chicago. Lowercasing first also means NASA comes back as Nasa.

Word's Capitalize Each Word and a spreadsheet's PROPER are the same shape of function under different names, which is why none of them is a substitute for a converter that carries the word list. The small-word list is the whole difficulty, and a text editor has no reason to ship one.

Which one should you actually use

If you have a house style, follow it. If you do not, these are the defaults worth adopting.

• Interface text, buttons, menus, form labels: sentence case. Every major design system agrees.
• Page headings and blog post titles: sentence case, unless you publish American news.
• Book, article and paper titles in a reference list: title case, in whichever style the publication asks for.
• Email subject lines: sentence case. Title case reads as marketing, which is where spam filters and readers both learned it.
• Anything all in capitals: nothing. Fix it. A block of capitals is slower to read, because it takes away the ascenders and descenders a reader uses to tell words apart, and it reads as shouting besides.

The measurements above were run once, by hand, on 29 August 2026. Web tools change without announcing it, so if a row here disagrees with what you see today, trust what you see.