Case Converter

Convert text between twelve casing styles, a line at a time, without it leaving the tab.

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What this tool does

Case Converter offers twelve styles from one list. Six are for prose — uppercase, lowercase, Title Case, Sentence case, aLtErNaTiNg and iNVERSE — and six rebuild the text as an identifier: camelCase, PascalCase, snake_case, kebab-case, CONSTANT_CASE and dot.case. The prose styles reshape the characters you gave them; the identifier styles take the words apart and put them back together.

That rebuilding follows two rules worth knowing. Words are split at case boundaries as well as at spaces, so parseHTMLResponse becomes parse-html-response and utf8Encoder becomes utf8_encoder, with digits staying attached to the letters they follow. Everything that is not a letter or a digit is then treated as a separator, punctuation and emoji included — "don't stop" comes back as don_t_stop, and [email protected] collapses to user_example_com. Accented and non-Latin letters survive the trip; café keeps its é. Nothing checks that the result is a legal identifier, so a line starting with a number keeps it: 2 fast 2 furious becomes 2Fast2Furious.

Title case and Sentence case both lowercase a word before recapitalising it, and that is the limitation to plan around. NASA comes back as Nasa, iPhone as Iphone, and O'Brien as O'brien, because there is no dictionary of names or acronyms behind any of this. Sentence case has two further blind spots: every full stop reads as the end of a sentence, so "went to the u.k. yesterday" comes back with Yesterday capitalised, and every standalone i is rewritten as I — right in English, wrong in Catalan or Polish where i is an ordinary word. All three are quick to repair by hand, but check the output before you ship it.

Everything here is done by the page you are reading. There is no request to a server and no copy of your text on our side, which is the practical reason to use it on a column of customer field names, an unreleased headline or an internal schema rather than pasting them into a site that processes text on someone else's machine.

How to use it

  1. Paste the text. Type into the input box or press Load sample. Empty input is refused with a message rather than quietly returning nothing.
  2. Pick a style from Convert to. Twelve options, each labelled in its own casing, so UPPER CASE, camelCase and dot.case show you what you will get.
  3. Decide how titles treat short words. With Title Case selected, "Keep short words lowercase in titles" leaves a, an, and, of, the, to, vs. and their relatives lowercase — unless the word opens or closes the line. Switch it off to capitalise every word.
  4. Leave the per-line checkbox alone. "Treat each line separately" is on by default and, as the code stands today, changes the output for none of the twelve styles except Sentence case: the other eleven already convert one line at a time whatever the box says. In Sentence case it affects only a line that begins with a space, whose first letter is left lowercase while the box is on. On is the sensible default.
  5. Copy the result. The output pane holds the converted text, with a count of the words converted and the style applied underneath.

Processing & privacy

Runs on your device. Your file is processed directly in this browser.

Common use cases

Matching a codebase's naming convention

Paste a list of field labels and get snake_case for a database, camelCase for JavaScript or CONSTANT_CASE for environment variables, one per line.

Rescuing a headline typed in caps lock

Uppercase text carries no word boundaries a reader can use. Title Case with the short-word option on restores them in a single pass, though any acronym or brand name in the line still has to be put back by hand afterwards.

Turning page titles into class names

kebab-case strips the punctuation and spaces out of a heading, which is the shape CSS classes, filenames and asset slugs expect.

Normalising an exported spreadsheet column

Column headings arrive in whatever casing the last person used. One conversion makes the whole set consistent before the import.

Toning down a shouty paragraph

Sentence case pulls a block written in title case or capitals back to ordinary prose, leaving the proper nouns to fix by eye.

Questions

Does any of my text leave this tab?
No. Case Converter is a plain text box wired to a function on this page — there is no file picker, no upload and no server call, and it keeps working with the network switched off.
Why did NASA turn into Nasa?
Title Case and Sentence case lowercase each word before capitalising its first letter, and neither keeps a list of acronyms or brand names. Anything with internal capitals — NASA, iPhone, MacDonald, O'Brien — loses them and has to be put back by hand.
Which words stay lowercase in Title Case?
A fixed list of twenty-three English minor words: a, an, and, as, at, but, by, en, for, if, in, nor, of, on, or, per, the, to, v, v., vs, vs. and via. A trailing full stop is stripped before the lookup, so v. and vs. behave exactly like v and vs. They are only left lowercase when they fall in the middle of a line, so a title that begins or ends with one still gets its capital.
What happens to punctuation in camelCase and snake_case?
It is dropped. Those styles keep only letters and digits, and treat everything else as a word boundary, so apostrophes, commas, slashes and @ signs all become separators. "Q1 report (final)" becomes q1_report_final.
Does it work with accents, or with Chinese and Arabic?
Yes for splitting and joining — letters outside the Latin alphabet are treated as word characters, so they survive into snake_case and kebab-case intact. Scripts without upper and lower forms simply pass through the casing styles unchanged, since there is no other case to convert them to.
Are hyphenated words handled?
Each part of a hyphenated compound gets its own capital in Title Case, so ten-year-old becomes Ten-Year-Old. With the short-word option on, minor words inside the compound stay down: state-of-the-art becomes State-of-the-Art.
What are alternating and inverse case for?
Alternating case flips between lower and upper across the letters, skipping anything that is not a letter as it counts — punctuation and digits included, so a1b2c becomes a1B2c. Inverse case swaps whatever case each letter already has. Both are novelty styles rather than editorial ones.

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