Case Converter

Title Case and Sentence case are not interchangeable, and picking the wrong one is the most visible formatting error in a document. Sentence case capitalises the first word and any proper nouns, and it is what the BBC, the Guardian, and most modern product interfaces use. Title Case capitalises the principal words and is standard for book titles, academic paper headings under APA and Chicago, and most US publications.

Strict Title Case does not capitalise every word. Articles (a, an, the), short conjunctions (and, but, or), and short prepositions (in, on, at, to, of) stay lowercase unless they are the first or last word. Automatic Title Case tools, including this one, capitalise every word because the alternative requires knowing the grammatical role of each word. Treat the output as a fast first pass and lowercase the small words yourself if you are writing to a style guide.

The four programming cases are not stylistic preferences, they are conventions that signal what a name is. camelCase is the default for variables and functions in JavaScript, Java, and Swift. PascalCase, the same thing with the first letter capitalised, marks classes, types, and React components in nearly every language that has both conventions. snake_case is the Python and Ruby standard for variables and functions, and it is also the near-universal convention for SQL column names and JSON keys in APIs written outside the JavaScript world. kebab-case cannot be used for identifiers in most languages because the hyphen reads as subtraction, which is exactly why it owns URLs, CSS class names, and file names.

Mixing conventions inside one codebase is the real cost. A JSON payload with both userId and user_name will silently break a deserialiser that expects one style, and case-insensitive filesystems on Windows and macOS will hide the problem until it reaches a Linux server.

Case conversion is not always reversible, and knowing where it loses information saves rework. Converting to UPPERCASE destroys the original capitalisation, so text that had proper nouns, acronyms, or camelCase identifiers in it cannot be restored by converting back to lowercase. Keep the original if you might need it.

A few specifics: acronyms like NASA, PDF, and HTML survive uppercasing but are mangled by Title Case and Sentence case, which turn them into Nasa and Pdf. Names with internal capitals such as McDonald, O'Brien, and iPhone are lowercased incorrectly by every automatic rule. And converting a sentence to snake_case or kebab-case replaces spaces with separators and drops punctuation, which is correct for a URL slug and wrong for prose. Convert, then read the result before you use it.