Case Lab

A case converter is a free online tool that changes the capitalization pattern of your text in one click — without retyping it. Paste a paragraph, a heading, or a variable name, and instantly get UPPERCASE, lowercase, Title Case, Sentence case, camelCase, PascalCase, snake_case, kebab-case, CONSTANT_CASE, aLtErNaTiNg, or InVeRsE. Writers use it to fix headings and rescue text typed with Caps Lock on; developers use it to convert naming conventions between programming languages.

camelCase joins words with no separator, lowercases the first word, and capitalizes the first letter of every following word — like helloWorld or userFirstName. The capital letters in the middle look like a camel's humps, hence the name. It is the standard convention for variable and function names in JavaScript and Java. This tool's camelCase card also detects word boundaries inside existing camelCase text, so helloWorld stays helloWorld and XML HttpRequest-style acronyms split correctly (XMLHttpRequest becomes xmlHttpRequest).

snake_case joins words with underscores and lowercases everything — like hello_world or user_first_name. It is the standard convention for variables and functions in Python and Ruby, and for column names in SQL databases. CONSTANT_CASE (also called SCREAMING_SNAKE_CASE) is its uppercase sibling, used for constants and environment variables — like MAX_RETRY_COUNT.

The only difference is the first letter: camelCase starts lowercase (helloWorld) while PascalCase capitalizes every word including the first (HelloWorld). camelCase is used for variables and functions; PascalCase is used for class names in most languages (JavaScript, Python, Java, C#). Both cards in this tool convert from any input format — spaces, underscores, hyphens, or an existing camelCase string.

Title Case capitalizes the first letter of every word (The Quick Brown Fox) and is used for headings and book titles. Sentence case capitalizes only the first letter of each sentence and lowercases the rest (The quick brown fox), which is the style of normal prose. Note: this tool's Title Case capitalizes every word literally, including short words like "and" or "the" — it does not apply APA/Chicago small-word rules, so style-guide-perfect titles may need a quick manual touch-up.

Follow the language you are writing in: Python, Ruby, and Rust use snake_case for variables and functions; JavaScript, Java, and Go use camelCase. CSS classes, URLs, and file names use kebab-case; constants and environment variables use CONSTANT_CASE; class names almost everywhere use PascalCase. The most common real-world need is converting between them when a Python backend sends user_id but the JavaScript frontend expects userId — that is exactly what the developer cards on this page are for.

Paste your text into the box above — the snake_case card updates live, no button needed. helloWorld becomes hello_world automatically. The converter detects lowercase-to-uppercase boundaries and acronym runs, so XMLHttpRequest correctly becomes xml_http_request (not x_m_l_http_request), and separators like spaces, hyphens, and dots are treated as word breaks too.

Paste the ALL-CAPS text into the box and read the Sentence case card: it lowercases everything, then capitalizes the first letter of each sentence. "HELLO WORLD. HOW ARE YOU?" becomes "Hello world. How are you?" in one step. As a bonus, the tool restores the English pronoun "I" (so "i think" becomes "I think"). For headings rather than prose, use the Title Case card instead.

Alternating case flips every other letter between lowercase and uppercase — hElLo WoRlD — and is also called sponge case or mocking case after the sarcastic SpongeBob meme. This tool starts with a lowercase letter (aLtErNaTiNg style) and only counts letters, so spaces, digits, and punctuation don't disturb the rhythm. InVeRsE case is its cousin: it swaps whatever case each letter already has.

Yes. All conversions are Unicode-aware: accented letters convert correctly (héllo becomes HÉLLO), and special mappings like the German ß becoming SS in UPPERCASE work as defined by the Unicode standard. Word boundaries are detected across scripts, so mixed-language text converts sensibly. One caveat: case mapping follows standard Unicode rules, not language-specific ones (for example, the Turkish dotted İ).

No. This tool runs 100% in your browser with JavaScript — your text never leaves the page, is never uploaded, and is never stored. You can even disconnect from the internet after the page loads and every conversion still works. That makes it safe for proprietary code, unpublished manuscripts, and private notes.

In Microsoft Word, select your text and use the Change Case button (Aa) on the Home tab, or press Shift+F3 to cycle cases. In Excel, use the formulas =UPPER(A1), =LOWER(A1), or =PROPER(A1) for title-style capitalization. For anything those built-ins can't do — camelCase, snake_case, kebab-case, alternating case, or converting a whole exported list at once — paste the text into this tool instead.

This tool converts free text and prose into 11 case styles with live stats. If you need to rename the keys inside a JSON object (for example, converting an API response from snake_case keys to camelCase keys while keeping the structure valid), use our dedicated JSON key case converter at nrtechstudio.com/tools/json-key-case-converter/ instead — it understands JSON syntax and won't break your data.

Yes — completely free, with no account, no sign-up, and no conversion limits. Every result card has its own copy button, you can copy all 11 conversions at once, or download them as a .txt file. Because everything runs locally in your browser, it also works offline once loaded.