Case converter

UPPERCASE, lowercase, Title or Sentence case. Free, no upload. 1 GB max · Up to 1 GB · Processed locally, never sent to a server.

Retyping a heading that arrived in block capitals, cleaning up a paragraph pasted out of a form where every letter is uppercase, turning a title into a file name with no spaces and no accents: these are still done by hand, character by character, far more often than they should be. This page offers seven transformations, each behind its own pill, applied to the text pasted into the top box.

The conversion goes through the browser’s locale-aware case functions. That detail changes the result: “café” becomes “CAFÉ”, “Zoë” becomes “ZOË”, “résumé” becomes “RÉSUMÉ”. Accents are kept on the capitals, where a rough conversion drops them. The German “straße” becomes “STRASSE”, the sharp s having no capital of its own and expanding into two letters instead.

The source text is never modified. The result is written into a second, read-only box, so you can try one transformation, look at it, try another on the same source, then copy whichever fits using the button under the result. Everything is computed inside the page, with no upload and no waiting, including on a text several pages long. Each click on a pill writes the name of the transformation and the number of words processed into the local history, never the text itself.

How to use it

  1. Paste the text to convert The top box stays your source for the whole session: it is not overwritten by the result, so you can run one attempt after another on it.
  2. Pick one of the seven pills UPPERCASE, lowercase, Sentence case, Title Case, iNVERT, snake_case and camelCase. One click is enough; there is no option and no confirmation button.
  3. Look at the bottom box It is read-only and holds the last result produced. A new pill replaces its content, never the content of the top box.
  4. Restore by hand what the machine cannot know Sentence case and Title Case drop everything to lowercase first: acronyms and product names such as NASA or iPhone come out damaged, and so does the pronoun “I” in mid-sentence.
  5. Copy the result The button under the output box puts its content on the clipboard, ready to paste into a document, a form field or a line of code.

The seven transformations in detail

UPPERCASE and lowercase apply case to the whole text, accents included in both directions. Sentence case first drops everything to lowercase, then raises a capital at the start and after each strong punctuation followed by a space; the space is required, so “hello.world” comes back as “Hello.world”. The pronoun “I” goes down with the rest and only comes back up when it opens a sentence: “Yesterday I called Ann” returns as “Yesterday i called ann”.

Title Case works the same way, then capitalises every word except a fixed list of thirty short ones, which stay in lowercase unless they open the text. iNVERT works character by character: capitals go down, lowercase goes up, digits, punctuation and spaces come out unchanged. snake_case and camelCase break the text apart, strip diacritical marks, drop everything to lowercase and replace the separators, the first with underscores, the second with a capital glued to the following word.

Accented letters, and what a round trip loses

The case functions are locale-aware, which is why accented letters survive in both directions. “CAFÉ” does not come back as “CAFE”, and names like “Zoë”, “Renée” or “Beyoncé” keep their marks when a headline goes up to capitals. Digits, punctuation and emoji pass through untouched.

Case conversion is not reversible, though. Send “NASA iPhone” up to capitals and back down and you get “nasa iphone”: the information is gone and no transformation restores it. The German sharp s behaves the same way, expanding into SS on the way up and never contracting again. Keep the original: that is what the top box is for. And if a technical field refuses anything outside plain ASCII, go through snake_case, which strips the marks, before going back up to capitals.

What Title Case cannot guess

The list of words left in lowercase holds thirty entries, ten of them English: the, of, a, an, and, or, to, in, on and for. Words that several style guides also lowercase are missing from it — with, from, by, at, over — so they take a capital, and “Gone with the Wind” comes back as “Gone With the Wind”. No fixed list can match every convention here, since one style guide lowercases every preposition while another capitalises those of four letters or more.

The remaining entries are French: de, du, des, le, la, les, en, sur and their neighbours. A French word inside an English title therefore stays down. “La La Land” comes back as “La la Land”, and “Sur La Table” as “Sur la Table”. Acronyms and product names do not survive the lowercase pass either: NASA becomes Nasa, iPhone becomes Iphone, PDF becomes Pdf. Internal capitals go the same way, which turns “McDonald” into “Mcdonald” and “O’Brien” into “O’brien”, the letter after an apostrophe never being raised.

snake_case and camelCase, for identifiers

Both transformations decompose each accented character to pull the diacritical mark off it: “é” becomes “e”, “ç” becomes “c”, so “Café Résumé & Co” gives “cafe_resume_co”. Characters that have no canonical decomposition, and that are not plain Latin letters, are treated as separators instead: “Encyclopædia” gives “encyclop_dia”, and the Danish name “Søren” gives “s_ren”. Apostrophes go the same way, being neither letter nor digit, so “Don’t Stop Believin’” gives “don_t_stop_believin”, the trailing underscore being trimmed off.

camelCase ends on a rule that removes everything before the first lowercase letter, so a text starting with a digit loses that digit and the letter that follows it: “5 tips for writers” comes out as “ipsForWriters”. Check the start of the result before making it a variable name. That rule works on the head only, so a trailing apostrophe survives in camelCase where snake_case trims it. For a web address, Google’s recommendations favour the hyphen over the underscore, and neither of these two produces one.

Frequently asked questions

Why does “NASA” come back as “Nasa”?

Because Sentence case and Title Case start by dropping the whole text to lowercase before raising the capitals they need. Acronyms are not recognised as such, so they are handled as ordinary words and have to be restored by hand afterwards.

Do accents survive the move to capitals?

Yes. The conversion uses the browser’s locale-aware case mapping, so “café” gives “CAFÉ” and “Zoë” gives “ZOË”, and nothing is lost on the way back down either. The German sharp s is the exception: it expands into SS going up and does not contract again.

How do I get “La La Land” out of Title Case?

By fixing it afterwards. The list of words kept in lowercase contains the French article “la”, with no way of knowing that here it belongs to a title in English. The automatic result is “La la Land”.

Why does “Søren” become “s_ren” in snake_case?

Stripping the marks works by decomposing characters, and the Danish o with stroke has no canonical decomposition. Being neither a plain letter nor a digit, it is treated as a separator. Write “Soren” before converting if you want to avoid the hole.

Can I convert only part of the text?

No, the transformation applies to the whole input box. Paste in only the passage concerned, convert it, then put it back into your document.

Does the result replace my original text?

Never. The two boxes are independent: the top one keeps your source, the bottom one receives the result and lets itself be overwritten as many times as you try pills.

Does Title Case follow AP or Chicago style?

Neither. It applies a fixed list of thirty short words that stay in lowercase, ten of them English — the, of, a, an, and, or, to, in, on and for — and capitalises everything else, so prepositions those guides also lowercase take a capital here: “Gone with the Wind” comes back as “Gone With the Wind”. No single list can satisfy both, since one guide lowercases every preposition while the other capitalises those of four letters or more, which leaves the final pass to you.

Is the text I paste sent anywhere?

No. All seven transformations are computed inside the page, with no upload and no waiting, including on a text several pages long. Each click writes the name of the transformation and the number of words processed into the local history, and never the text itself.

How do I turn a heading that arrived in block capitals back to normal capitalisation?

Paste it into the top box and click Sentence case, which drops the whole text to lowercase and then raises a capital at the start and after each strong punctuation followed by a space. That trailing space is required, so “hello.world” comes back as “Hello.world”. What the capitals destroyed does not return on its own: proper nouns and the pronoun “I” in mid-sentence have to be put back by hand, since nothing in the text says they were ever capitals.

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