Two headlines can say the exact same thing and still look different depending on which capitalization style is used: "How to Convert PX to REM" (Title Case) versus "How to convert px to rem" (Sentence case). Neither is "correct" universally — it depends on where the text is going.
What Title Case Actually Does
Title Case capitalizes the first letter of most words in a heading, traditionally lowercasing minor words like "a," "the," "of," and "and" (strict editorial style guides follow this rule closely; a simpler version capitalizes every word, which is what many quick tools and the CSS text-transform: capitalize property do).
How the Major Style Guides Differ
Every major style guide capitalizes the first and last word and the “major” words (nouns, verbs, adjectives, adverbs, pronouns). Where they differ is in the small words:
| Style guide | Lowercases | Example |
|---|---|---|
| Chicago Manual of Style | Articles, coordinating conjunctions (and, but, or, for, nor) and prepositions of any length | How to Choose between Title Case and Sentence Case |
| AP Stylebook | Articles, conjunctions and prepositions of three letters or fewer | How to Choose Between Title Case and Sentence Case |
| APA Style | Minor words of three letters or fewer (short conjunctions, articles, short prepositions) | How to Choose Between Title Case and Sentence Case |
| Capitalize every word | Nothing | How To Choose Between Title Case And Sentence Case |
The difference here is the seven-letter preposition “between”: Chicago lowercases it, while AP and APA capitalize it because it has four or more letters. If you write for a publication, follow its guide; if you set your own rules, pick one guide and stick with it.
What Sentence Case Actually Does
Sentence case capitalizes only the first letter of the sentence (and proper nouns), the same way normal prose is written. It reads as more casual and closer to natural writing.
The one thing people get wrong with sentence case is proper nouns and acronyms. They keep their normal capitals: “Export your video from Google Chrome as a WebM file” — not “Export your video from google chrome as a webm file.” Brand names with unusual capitals, such as “iPhone” or “YouTube,” keep them too.
The Same Headings, Both Ways
| Title Case (AP style) | Sentence case |
|---|---|
| How to Use VH and VW in CSS | How to use VH and VW in CSS |
| A Beginner’s Guide to Color Formats | A beginner’s guide to color formats |
| Why Your Word Count Matters for SEO | Why your word count matters for SEO |
| Is It Safe to Record Your Screen Online? | Is it safe to record your screen online? |
Notice that short verbs like “Is” stay capitalized in Title Case — the small-word rule applies to articles, conjunctions and prepositions, not to every short word.
Where Each One Is Expected
- Title Case — blog post titles, book titles, formal headings, print publications, many marketing headlines.
- Sentence case — UI buttons and labels (most modern design systems, including Google's Material Design, prefer sentence case for buttons — "Save changes" rather than "Save Changes"), chat interfaces, informal writing.
Why This Became a Real Design Decision
Design systems shifted toward sentence case for interface text over the last decade because it reads faster and feels less "shouty" than Title Case in dense UIs with many buttons and labels — a screen full of Title Case buttons can end up looking more like a printed poster than a piece of software.
Consistency Matters More Than the Choice Itself
Whichever style you pick, the biggest readability problem is mixing both inconsistently across the same product or document — some headings in Title Case, others in Sentence case, with no clear rule. Pick one per context (e.g. Title Case for page titles, sentence case for buttons) and apply it consistently.
A simple way to make it stick is a one-line rule in your style notes, for example:
- Page titles and article headlines: Title Case (AP).
- Subheadings inside articles: sentence case.
- Buttons, menu items, form labels and error messages: sentence case.
- Proper nouns, product names and acronyms: always as officially written.
Using a Case Converter Without Creating New Errors
A case converter saves time, but automatic conversion can’t know which words are names or acronyms. Our Case Converter’s Title Case button follows Chicago/APA-style rules: it capitalizes major words, keeps short words such as “of”, “the” and “to” lowercase in the middle of a title, and leaves acronyms like CSS and names like iPhone exactly as you typed them. Its Sentence case button capitalizes the first letter of each sentence and also keeps acronyms and mixed-case names. Proper nouns typed in lowercase (“london”, “google”) can’t be detected, though, so a quick review afterwards is still part of the job:
- Paste your heading and click Title Case or Sentence case.
- For Title Case, lowercase the minor words your style guide requires (a, an, the, and, of, to, in…), unless they are the first or last word.
- Fix acronyms you typed in lowercase: “how to convert px to rem” comes out as “How to Convert Px to Rem” and needs to become “How to Convert PX to REM”. Typing them in capitals before converting avoids this.
- Restore proper nouns and brand names, especially in sentence case: “google chrome” back to “Google Chrome”.
- Click Copy Text and paste the result where you need it.
Converters are especially useful for fixing text that arrived in ALL CAPS — from a spreadsheet export or a pasted email subject — where retyping would be slow.
Case in CSS: Style, Don’t Retype
On websites, it’s often better to type text normally and let CSS change how it looks:
.nav-link { text-transform: uppercase; }
.card-title { text-transform: capitalize; } /* capitalizes every word */This keeps the original text intact in the HTML, so you can change the design later without editing content, and copied text keeps its normal capitals. Just remember that capitalize is the “every word” style, not proper editorial Title Case, and it won’t lowercase words you typed in capitals.
Does Capitalization Affect SEO?
Search engines match words regardless of case, so “Title Case” and “title case” are treated as the same words. The choice is about readability and consistency in search results and on your site, not rankings. What matters more is a clear, accurate title of a sensible length — you can check headline and description length with our Word Counter, and our article on why word count matters for SEO covers length for whole pages.
Frequently Asked Questions
Should email subject lines use Title Case or sentence case?
Either works, as long as you are consistent. Sentence case tends to feel more personal, like a message from a person, while Title Case feels more like a newsletter or announcement.
Do I capitalize the word after a colon in a title?
In Title Case, yes — the major style guides capitalize the first word after a colon in a heading, as in “Aspect Ratios: A Quick Guide.” In sentence case, many guides (including APA) also capitalize it, but house styles vary.
How are hyphenated words handled in Title Case?
Usually both parts are capitalized when they are major words, as in “Step-by-Step Guide” or “Long-Term Plan.” Short minor words within a compound, like “by” in “Step-by-Step,” follow your style guide’s small-word rule, and guides differ here.
Is ALL CAPS ever a good choice?
For very short labels, such as a small tag or badge, it can work. For anything longer than a few words it’s harder to read, because every word has the same rectangular outline. Use CSS text-transform if you want the look without retyping.
Try it yourself: paste a few of your current headings into the Case Converter, convert them to Title Case and to Sentence case, fix any acronyms or names, and decide which style reads better for your site — then apply it to every heading of that type.