Case Converter

How to use it

1. Paste or type your text into the left box.
2. Pick a case from the row above it. Writing cases are for prose and headlines; code cases are for variable names, file names and slugs.
3. If the case has an option — a style guide for Title Case, acronym handling for sentence case — it appears directly under the row. Nothing else does.
4. Press Copy. The result is already on your clipboard.

What each case does

Sentence case

The first letter of every sentence is capitalized and everything else is lowered, the way ordinary prose is written. A sentence ends at a full stop, question mark or exclamation mark, and every new line starts a new sentence. The lone pronoun i becomes I, as do i'm, i've, i'll and i'd.

Two things that trip up simpler tools are handled here. Abbreviations such as Dr., Mr., vs., etc., e.g. and a.m. do not end a sentence, so the word after them is left alone. And with Keep acronyms as typed on, words that are already ALL CAPS — NASA, HTML, USA — stay that way instead of being flattened to Nasa, Html and Usa.

Title Case

Major words are capitalized and minor words — articles, short conjunctions, prepositions — are lowered. Which words count as minor depends on the style guide, and that is what the Style guide option controls. All four styles agree on the basics: the first and last word are always capitalized, and so is the first word after a colon or an em dash.

Capitalized Case

Every word gets a capital letter, including articles and prepositions, and including both halves of a hyphenated word. It is the right choice when you want every word to stand out and do not care about a style guide.

UPPERCASE, lowercase, aLtErNaTiNg cAsE and iNVERSE cASE

Uppercase and lowercase do what they say. Alternating case switches between lower and upper on every character, and Start with a capital flips which one comes first. Inverse case swaps every letter: capitals become small and small become capitals, which is the fastest way to undo an accidental Caps Lock.

Code cases

The seven code cases break your text into words and rebuild each line as an identifier: camelCase, PascalCase, snake_case, CONSTANT_CASE, kebab-case, dot.case and Train-Case. Word boundaries are found at spaces, punctuation, existing underscores and hyphens, camelCase humps, acronym edges (HTMLParser is HTML and Parser) and where letters meet digits. Each line is converted on its own, so you can paste a whole column of names at once.

Title case: how the style guides differ

"Title case" is not one rule. Publishers disagree about prepositions and conjunctions, and the disagreements are exactly the words people get wrong. This is what the four supported guides do with the title a walk through the woods with friends, yet so far:

Notice that Far is capitalized in every style, even where the "so" before it is lowered: the last word of a title is always capitalized. Chicago is the odd one out on Yet So — it lowers only and, but, for, or and nor, while the other three lower all seven coordinating conjunctions. Hyphenated words are capitalized on both sides (Well-Known) unless the second half is a minor word for that style (Run-in).

Why acronyms need special treatment

A naive sentence-case converter lowers everything after the first letter, which turns "the NASA report on HTML5" into "the nasa report on html5". Most tools do exactly this. Here, any word that is already entirely upper case and at least two letters long is treated as an acronym and left alone, in sentence case, Title Case and Capitalized Case.

There is one deliberate exception. If a line is entirely upper case — the classic pasted-from-a-form SHOUTING — then every word on it would look like an acronym and nothing would change. So on any line where three quarters or more of the letters are already capitals, acronym protection switches itself off and that line is converted normally. It is judged line by line, so a pasted list can mix JOHN SMITH (which becomes John Smith) with a line mentioning NASA (which keeps it). You can also turn protection off yourself with the checkbox.

What people use it for

Fixing a headline for a style guide

Paste the headline, choose Title Case, pick the guide your publication or course uses. The help text under the selector tells you the rule it is applying, so you can explain the result to an editor if you need to.

Rescuing text typed with Caps Lock on

Sentence case turns an all-caps paragraph back into normal prose in one click, including the capital after each full stop. If only one word is wrong, iNVERSE cASE flips just that word.

Renaming variables, files and slugs

Paste userAccountId and choose snake_case to get user_account_id; choose kebab-case for a URL slug or CONSTANT_CASE for an environment variable. A column of names converts line by line, so you can rename a whole set at once.

Normalising names from a spreadsheet

Exported data often arrives as JOHN SMITH or john smith. Capitalized Case makes every name John Smith, one per line.

Questions

Does my text get uploaded anywhere?

No. The conversion is a JavaScript function running in your browser. Nothing you paste leaves the page, which you can confirm from the Network tab of your browser's developer tools. See our Privacy Policy for the full position.

Why did sentence case not capitalize a proper name?

Because it cannot know which words are names. "meet john in paris" becomes "Meet john in paris" — correct sentence capitalization, but no tool can tell that john and paris are names without a dictionary of every name and place. Fix those by hand, or use Capitalized Case if every word in your text is a name.

Which title case style should I use?

Use whatever your publisher, journal or course asks for. If nobody has told you, APA is the safest default: its four-letter rule is easy to apply consistently and matches what most people expect a headline to look like. Chicago is the usual choice for books; AP for news; MLA for humanities coursework.

Does it handle languages other than English?

Upper, lower, sentence and inverse case work for any script that has letter case: accented Latin, Greek, Cyrillic and so on. Title Case applies English style-guide rules, so French or German articles will be capitalized as ordinary words.

Are my settings remembered?

Yes, in this browser only. The mode and its options are stored locally so the tool opens the way you left it. Clearing site data resets it.