What this does

Paste text, choose one of twelve cases, and the converted version appears underneath as you type. It covers the two jobs people actually come for: tidying up prose — sentence case, title case, fixing something typed with caps lock on — and reshaping names for code, wherecamelCase, snake_case, kebab-case andCONSTANT_CASE all describe the same words in different clothes.

Title case done properly

Capitalising every word is not title case. Style guides keep articles, conjunctions and short prepositions in lower case unless they open or close the title, which is why it'sThe Lord of the Rings rather than The Lord Of The Rings. This tool follows that rule, and also capitalises the word after a colon, since a subtitle starts a new phrase.

Acronyms survive too. the NASA report becomes The NASA Report, notThe Nasa Report — any all-capital word of two letters or more is left alone. The one exception is text that's entirely in capitals, where there's no way to tell an acronym from shouting; that gets flattened to lower case first and rebuilt, so a caps-lock accident comes out properly cased.

How the code cases split words

Turning getHTTPResponse2 into get_http_response_2 means finding word boundaries where there are no spaces. The rule used here breaks on punctuation and spaces, on the change from lower case to capital, and at the end of a run of capitals — soHTTPResponse splits into HTTP and Response rather than landing as one lump or splitting into individual letters. Digits count as their own word.

The four identifier styles convert line by line. Paste a column of forty product names and you get forty converted lines back, not one enormous identifier. On a single line it makes no difference.

The twelve cases

Sentence case — capital at the start of each sentence, the rest left alone.
lower case and UPPER CASE — every character, no exceptions.
Title Case — headline style, with small words kept down.
camelCase — first word lower, the rest capitalised. Variables in JavaScript, Java and Swift.
PascalCase — every word capitalised, no separators. Classes and components.
snake_case — lower case joined by underscores. Python, Ruby, database columns.
CONSTANT_CASE — snake case in capitals. Environment variables and constants.
kebab-case — lower case joined by hyphens. URLs, CSS classes, file names.
dot.case — lower case joined by dots. Config keys and namespaces.
tOGGLE cASE — every letter flipped to the opposite case.
aLtErNaTiNg — alternating letters, for when you're being sarcastic on the internet.

Which one does my language want?

Conventions differ, and following them is most of what makes code look native. JavaScript and Java use camelCase for variables and PascalCase for classes. Python and Ruby use snake_case for almost everything and PascalCase for classes. Go uses PascalCase for anything exported and camelCase for anything private. CSS classes and URL slugs use kebab-case, because both treat the underscore as awkward and the hyphen as natural. Environment variables are CONSTANT_CASE almost everywhere.

Is it private?

Yes. The conversion is done by JavaScript inside this page — the text you paste never leaves your device, isn't logged, and isn't sent to a server, because there's no server involved. You can disconnect from the internet after the page loads and it will keep working.

Frequently asked questions

Does it keep my line breaks?

Always. Every conversion preserves the line structure you pasted in, which is what makes it usable on a list rather than a sentence.

Can it handle accents and other alphabets?

Yes — the word splitting uses Unicode letter classes, so accented Latin, Greek and Cyrillic all convert case correctly. Scripts without upper and lower case, such as Chinese, Japanese and Arabic, are passed through untouched, which is the correct behaviour: there is no other case to convert them to.

Why did sentence case capitalise a lone "i"?

Because in English it's a word rather than a letter and always takes a capital. If you're working in a language where a standalone "i" is a normal lower-case word, use lower case instead and capitalise sentence openings yourself.