Case converter
Convert text between upper, lower, title, sentence, camel, Pascal, snake, kebab and constant case, plus alternating and inverse case.
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The cases, and where each belongs
| Case | Example | Used for |
|---|---|---|
| UPPER CASE | HELLO WORLD | Acronyms, emphasis, legal headings |
| lower case | hello world | Normalising input, URLs, tags |
| Title Case | Hello World | Headlines, book and article titles |
| Sentence case | Hello world | Body prose, UI labels, buttons |
| camelCase | helloWorld | JS/Java variables and functions |
| PascalCase | HelloWorld | Classes, React components, C# methods |
| snake_case | hello_world | Python, Ruby, SQL columns |
| kebab-case | hello-world | URLs, CSS classes, HTML attributes |
| CONSTANT_CASE | HELLO_WORLD | Environment variables, constants |
| aLtErNaTiNg | hElLo WoRlD | Mocking tone in memes |
| iNVERSE | hELLO wORLD | Fixing accidental caps-lock text |
How the programming cases split words
Converting getUserName to snake_case requires knowing where the words are. The splitter inserts a boundary before any capital letter that follows a lowercase letter or digit, then splits on spaces, hyphens, underscores and dots.
So getUserName, get-user-name, get user name and GET_USER_NAME all reduce to the same three tokens and convert identically. This means you can move between any two conventions in one step without an intermediate pass.
One caveat: consecutive capitals are treated as a single token, so parseHTMLDocument becomes parse_htmldocument rather than parse_html_document. Acronym handling has no universally agreed rule, and every library makes a different choice here.
Title Case is not one thing
The three widely used style guides disagree:
- AP style lowercases prepositions of three letters or fewer.
- Chicago style lowercases all prepositions regardless of length, so “Notes on a Scandal” keeps “on” lowercase.
- APA style capitalises words of four or more letters, including prepositions.
This converter follows the AP-leaning convention, which is the most common in web publishing. For anything going to a publisher, verify against their guide.
Sentence case for interfaces
Most modern design systems - including Google’s Material and Apple’s Human Interface Guidelines - specify sentence case for buttons, labels and headings. It reads faster, handles long strings better, and translates more gracefully, since many languages have no equivalent of English title case.
If you are converting an interface from Title Case to sentence case, expect to fix proper nouns and product names by hand afterwards.
Fixing caps-lock accidents
Inverse case is genuinely useful once: you typed a sentence with caps lock on and Shift held, producing hELLO wORLD. Inverse case restores it exactly. Upper or lower case would destroy the original capitalisation instead.
Common questions
Which words stay lowercase in Title Case?
This converter leaves articles, coordinating conjunctions and short prepositions lowercase unless they are the first or last word - a, an, the, and, but, or, for, nor, at, by, in, of, on, to, up, via, as, from, into, over, with. That follows the common AP and Chicago approach. Note that style guides genuinely disagree, particularly on prepositions of four or more letters, so check your house style for published work.
What is the difference between camelCase and PascalCase?
Only the first letter. camelCase starts lowercase (userName), PascalCase starts uppercase (UserName). By convention JavaScript uses camelCase for variables and functions and PascalCase for classes and components, while C# uses PascalCase for methods too.
Will it handle text that is already in a mixed case?
Yes. The programming cases split on capital letters as well as spaces, hyphens, underscores and dots, so getUserName, get-user-name and get_user_name all convert to the same result in any target case.
Why did Sentence case not capitalise a name?
Sentence case capitalises the first letter after each sentence-ending punctuation mark and lowercases everything else. It cannot know that "paris" is a proper noun. Proper nouns need a manual pass afterwards.
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