Case Converter

Nine formats, computed from the same input

Type once and every card below the box fills in at the same time. There is no convert button and no format picker, because showing all nine at once is faster than choosing, especially when you are not sure which convention a codebase uses. The nine are UPPERCASE, lowercase, Title Case, Sentence case, camelCase, PascalCase, snake_case, kebab-case and CONSTANT_CASE.

Two of them are trivial. UPPERCASE and lowercase apply a single transformation to the raw string, so punctuation, line breaks and blank lines all survive untouched. The other seven work differently, and the difference is worth understanding before you paste something important.

How the tool decides where words begin

The seven programmer-style formats first break your text into a list of words. The rule is:

• Insert a boundary where a lowercase letter or digit is followed by a capital, so myVariable becomes two words.
• Insert a boundary inside a run of capitals where the last capital starts a new lowercase word, so HTMLDocument becomes HTML and Document rather than one blob.
• Split the result on spaces, tabs, line breaks, underscores and hyphens.

Put parseHTMLDocument in and you get parse_html_document, parse-html-document, PARSE_HTML_DOCUMENT and parseHtmlDocument. The acronym is found correctly, but it is flattened to Html in the camel, Pascal and Title outputs, because those formats lowercase everything after the first letter of each word. If your house style is parseHTMLDocument rather than parseHtmlDocument, this tool will not preserve it and you will need to restore the capitals yourself.

Acronyms in ordinary prose

The same flattening bites on real sentences. Feed in NASA budget and Title Case returns Nasa Budget. There is no dictionary of acronyms behind this, and there cannot be a reliable one, because US is a country and us is a pronoun. CONSTANT_CASE and UPPERCASE keep NASA intact, so if you are preparing a headline containing initialisms, take the Title Case output and put the capitals back by hand.

What Title Case and Sentence case actually do

Title Case here capitalises every single word. the lord of the rings becomes The Lord Of The Rings. Editorial style guides would give you The Lord of the Rings, lowercasing short prepositions, articles and conjunctions unless they open or close the title. This tool does not apply that rule, and the guides disagree with each other about which words qualify anyway. Treat the output as a starting point for a headline, not a finished one.

Sentence case lowercases the whole input, then capitalises the first character of the string and any character that follows a full stop, exclamation mark or question mark plus whitespace. Two consequences follow. Proper nouns are destroyed: Sydney comes back as sydney, and the pronoun I comes back as i. And a full stop used in an abbreviation triggers a false capital, so e.g. this becomes e.g. This. Sentence case is at its best on text that was accidentally typed in caps lock, which is exactly the job most people bring it.

Two gotchas that catch people out

First, punctuation is not stripped. The word splitter only breaks on whitespace, underscores and hyphens, so a comma or a full stop stays attached to the word it touches. Hello, world! produces hello,_world! in snake_case. If you are generating identifiers, clean the punctuation out of the input first.

Second, line breaks do not survive the seven word-based formats. Because line breaks count as word separators and the words are rejoined with a single space, underscore or hyphen, a three paragraph block pasted into the box comes back as one continuous run in Title Case. UPPERCASE and lowercase are the only two outputs that keep your paragraph structure, so use those when you are reformatting a document rather than a name.

When a different tool fits better

If what you actually want is a readability or length check on the text rather than a casing change, Word Counter gives you counts and reading time, and Readability Checker scores the prose. If you are comparing a renamed file against the original to confirm only the casing moved, Text Diff will show you line by line. For flipping character order rather than character case, use Reverse Text.

Frequently asked

Why did my acronym turn into Html or Nasa?

Title Case, camelCase and PascalCase lowercase every character after the first letter of each word, and there is no acronym dictionary. The word boundary is detected correctly, but the internal capitals are lost. Restore them manually, or use CONSTANT_CASE if all-caps is acceptable.

Why does Title Case capitalise "of" and "the"?

Because it capitalises every word without exception. Proper editorial title case keeps short function words lowercase in the middle of a title, and this tool does not implement that rule. Fix those words after copying.

Why did my paragraphs collapse into one line?

Line breaks are treated as word separators by the seven formats that rebuild the text word by word, so they are replaced by the joining character. Only UPPERCASE and lowercase preserve the original layout.

What is the difference between camelCase and PascalCase?

Only the first character. camelCase leaves the opening word lowercase, giving myVariableName, while PascalCase capitalises it, giving MyVariableName. Most languages use camelCase for variables and PascalCase for class and type names.

Is my text sent anywhere?

No. Every conversion happens in the page as you type, and nothing you paste is transmitted or stored.