Text case converter

The cases, and where each belongs

• Sentence case — capital at the start of each sentence. Normal prose.
• Title Case — capitals on principal words. Headlines and headings.
• camelCase — JavaScript variables, JSON keys, Java methods.
• PascalCase — class and component names in most languages.
• snake_case — Python, Ruby, SQL column names.
• kebab-case — URLs, CSS classes, filenames.
• CONSTANT_CASE — constants and environment variables.

Title case is not "capitalise everything"

This is where naive converters get it wrong and produce headings that read like a ransom note. Real title case leaves short function words lowercase — articles, coordinating conjunctions and short prepositions — unless they are the first or last word.

So the lord of the rings becomes The Lord of the Rings, not The Lord Of The Rings. The implementation here keeps a list of those minor words and always capitalises the first and last regardless, which is the rule the major style guides share.

Converting between programming cases

Word boundaries are detected from spaces, underscores and hyphens together, so user_first_name, user-first-name and user first name all convert to userFirstName equally well. That makes this practical for renaming API fields when moving between a snake_case backend and a camelCase frontend.

Alternating case

The toggle option inverts each character's existing case. It is included because people ask for it; it has no formal use beyond sarcasm on the internet.

A note on uppercase

Converting a whole heading to uppercase is a formatting decision better made in CSS with text-transform than by changing the text itself. Text stored in capitals cannot be un-capitalised reliably — the original casing of proper nouns is gone — and screen readers sometimes announce all-caps words letter by letter. Convert here when the capitals belong to the content; use CSS when they belong to the design.

Related

For URLs specifically, the slug generator handles accents and punctuation as well as case.