Case Converter – Change Text to Upper, Lower, Title or Sentence Case

A case converter fixes text that was typed with Caps Lock on, capitalises headlines properly, or reformats a phrase into the naming style a programming language expects. Paste the text once and every variant is generated at the same time – no menus, no reloads.

The converter is Unicode-aware, so accented letters (é, ñ, ü) and non-Latin alphabets are handled correctly, and it treats hyphens and apostrophes sensibly in Title Case.

UPPERCASE and lowercase are self-explanatory. Title Case capitalises the first letter of every word, the style used for headlines and book titles (this simple version capitalises every word; house styles often leave "a", "the" and "of" lower-case). Sentence case capitalises only the first letter of each sentence, as in normal prose. Alternating case swaps case letter by letter and is the basis of the "mocking SpongeBob" meme; inverse case flips whatever case the text already has.

Developers use naming conventions to make identifiers readable without spaces. camelCase (firstWord lower, later words capitalised) is standard in JavaScript and Java; PascalCase (every word capitalised) names classes and React components; snake_case is Python and Ruby convention; kebab-case is used for URLs, CSS classes and file names; CONSTANT_CASE marks constants and environment variables; dot.case appears in configuration keys. The converter strips punctuation and splits on spaces, so "User profile ID" becomes userProfileId, user_profile_id or user-profile-id as needed.

The most common real-world use is rescuing text typed in all capitals: paste it, copy the Sentence case version, and fix any proper nouns by hand. For headlines, Title Case gives a consistent look across a site or document. Editors often paste a whole article to normalise mixed capitalisation before publishing.

Sentence case capitalises after a period, question mark or exclamation mark followed by a space; abbreviations like "e.g." can therefore trigger an unwanted capital – check the output. Title Case does not know proper nouns or acronyms (NASA becomes Nasa), so review names and acronyms after converting. Everything runs locally in your browser; the text is never sent anywhere.