Online Case Converter for Text and Code Identifiers

UPPERCASE applies JavaScript's toUpperCase() and lowercase applies toLowerCase() to the whole string; whitespace, punctuation, and line breaks remain while cased letters convert. Neither removes accents, punctuation, or spaces, so lowercase does not create a URL slug by itself — choose kebab-case for a separator transformation.

The Title Case option finds every non-whitespace token, uppercases its first character, and lowercases the remainder. This is simple token capitalization, not publication-style title casing: it does not keep short words lowercase and does not preserve acronyms, and hyphenated content stays one token:

building an API with JSON  →  Building An Api With Json
state-of-the-art design    →  State-of-the-art Design

Sentence case first lowercases the entire input, then capitalizes an ASCII letter at the beginning of the text after optional whitespace, at the beginning of a new line, or after ., !, or ? followed by whitespace. Because all text is lowercased first, proper nouns and acronyms must be restored, and a sentence starting with a quotation mark, digit, or non-Latin script may not capitalize as expected:

HELLO WORLD. THIS IS A TEST!  →  Hello world. This is a test!
OPENAI RELEASED AN API.       →  Openai released an api.

camelCase, PascalCase, snake_case, kebab-case, and CONSTANT_CASE share one word splitter. For each line it inserts a space between a lowercase/digit and a following uppercase, separates an acronym from a following capitalized word, replaces underscore and hyphen runs with spaces, trims, and splits on whitespace. camelCase lowercases the first word and capitalizes each later word; PascalCase capitalizes every word; snake/kebab lowercase and join with _ or -; CONSTANT_CASE uppercases and joins with _:

Customer_Profile-Image  →  customerProfileImage   (camelCase)
HTTPResponseCode        →  httpResponseCode       (camelCase)
XMLHttpRequest          →  XmlHttpRequest         (PascalCase)
accountDisplayName      →  account_display_name   (snake_case)
Summer Sale Landing     →  summer-sale-landing    (kebab-case)
maximumRetryCount       →  MAXIMUM_RETRY_COUNT    (CONSTANT_CASE)

Acronyms are normalized like ordinary words, so XML can become Xml — review project conventions such as URLParser versus UrlParser. Punctuation other than _ and - is not removed, so a comma or slash can remain attached to a word and produce an invalid identifier. Because kebab-case uses -, it is usually not a valid variable name in languages that read - as subtraction. Sanitize punctuation according to the destination rather than assuming the converter validates it.

All modes retain line breaks. Upper, lower, title, and sentence case operate across the full string while preserving newlines; identifier-style modes split on \n, convert each line independently, and join again. Blank lines remain blank, and within each nonblank identifier line, multiple separators collapse into the chosen join character:

Customer Name      →  customer_name
Account Status     →  account_status
Created At         →  created_at

Both input and output show live counts. The word count trims text, splits on runs of whitespace, and counts non-empty tokens — so a hyphenated term with no spaces counts as one word even though structured-case conversion can split it into multiple detected words. The character count is JavaScript string .length, which counts UTF-16 code units including spaces, punctuation, and line breaks, so many emoji and some less-common characters count as two or more. Counts are useful for quick comparison but are not linguistic segmentation or Unicode grapheme counts.

JavaScript's default toUpperCase() and toLowerCase() apply Unicode case mappings but are not tailored to a selected locale. Languages with context- or locale-sensitive casing can produce results different from editorial expectations — for example, the dotted and dotless forms of the letter I in Turkish. Case conversion can also change string length: German ß can uppercase to SS, so output character counts may differ even when separators are unchanged.

The structured-case boundary expressions primarily recognize ASCII [a-z], [A-Z], and digits, so case transitions in other scripts may not split into words. Use locale-aware language processing for internationalized publishing workflows.

kebab-case is a useful starting format for URLs, but a production slug pipeline should also decide whether to remove or transliterate accents, which punctuation is allowed, how to handle apostrophes and symbols, maximum length, uniqueness suffixes, reserved paths, stop-word policy, and redirects when a slug changes. Never change a live URL merely for capitalization without planning redirects and canonical links.

Naming styles communicate convention, but renaming a symbol can be a breaking change. Before replacing identifiers, update every reference, preserve serialized/API field contracts, check reflection and string-based lookups, run type checking and tests, and review database migrations. The tool is a text transformer, not a language-aware refactoring engine — it cannot distinguish a variable from a string literal, comment, external API property, or reserved keyword.

Conversion and counting use plain JavaScript in the browser and require no remote text-processing service. The tool works with pasted text rather than file uploads.

Text can still contain private names, internal identifiers, unpublished copy, or credentials. Avoid pasting secrets, use a trusted device, and consider clipboard history when copying output. Client-side transformation does not validate or anonymize the content.