Case Converter

Case Converter: How It Works

Changing text between cases is trivial for a machine and surprisingly opinionated for a human, because title case is not one rule but several competing ones. This converter handles the mechanical transformations and this page covers which convention to apply where.

The transformations

Case	Example	Used for
UPPERCASE	THE QUICK BROWN FOX	Constants, acronyms, emphasis (sparingly)
lowercase	the quick brown fox	URLs, email addresses, tags, normalisation
Title Case	The Quick Brown Fox	Headlines, book and article titles
Sentence case	The quick brown fox	Body text, UI labels, most modern headlines
camelCase	theQuickBrownFox	JavaScript and Java variables
PascalCase	TheQuickBrownFox	Class names, React components
snake_case	the_quick_brown_fox	Python, Ruby, database columns
kebab-case	the-quick-brown-fox	URLs, CSS classes, filenames

Title case is not one rule

Style guides genuinely disagree, and the disagreements are about small words.

Guide	Capitalises
AP	Words of four letters or more; all principal words
Chicago	All words except articles, short prepositions and conjunctions
APA	Words of four letters or more, plus all major words
MLA	All principal words regardless of length

All four capitalise the first and last word regardless. Under AP, 'A Guide to the Art of War' keeps 'to' and 'the' lowercase; under MLA the same title capitalises 'To'. There is no correct answer outside a chosen style guide — pick one and be consistent, which matters far more than which you pick.

Sentence case has been steadily replacing title case in interfaces and increasingly in headlines. It is easier to read, easier to apply consistently, and avoids the small-word problem entirely.

Cases that carry meaning in code

Programming conventions are not decoration; deviating from them makes code look wrong to anyone reading it. JavaScript uses camelCase for variables and PascalCase for classes and components. Python uses snake_case for variables and functions, PascalCase for classes, and SCREAMING_SNAKE_CASE for constants. CSS uses kebab-case. Databases conventionally use snake_case, partly because unquoted identifiers are case-folded by many engines.

The characters that break naive conversion

Turkish dotless i. Uppercasing 'i' in Turkish gives 'İ', not 'I'. Locale-unaware conversion has broken real authentication systems.
German ß uppercases to 'SS' — one character becoming two.
Acronyms. Naive title case turns 'NASA' into 'Nasa' and 'iPhone' into 'IPhone'.
Names. McDonald, O'Brien, van der Berg and de la Cruz all defy simple capitalisation rules.

For this reason, never case-normalise a person's name for storage. Store what they typed. Case-fold only for comparison, and use your language's locale-aware function when you do.

Frequently Asked Questions

Which title case rule is correct?

None universally — AP, Chicago, APA and MLA disagree about articles and short prepositions. All capitalise the first and last word. Choose one guide and apply it consistently; consistency matters more than the choice.

Should I use title case or sentence case for headings?

Sentence case is now the more common choice in interfaces and increasingly in editorial writing. It reads more naturally, is easier to apply consistently, and sidesteps the small-word disagreements entirely.

What is the difference between camelCase and PascalCase?

Only the first character. camelCase starts lowercase and is used for variables and functions; PascalCase starts uppercase and is used for classes, types and React components.

Why do acronyms get mangled by case conversion?

Automatic title case has no way to know that NASA is an acronym and not a word, so it produces 'Nasa'. Brand names with internal capitals like iPhone and eBay have the same problem. These need manual correction.

Should I normalise names to title case in a database?

No. Store exactly what the person entered. Automatic capitalisation breaks McDonald, O'Brien, van der Berg and many others. Case-fold only when comparing values, never when storing them.

Why can uppercasing break in some languages?

Case rules are locale-specific. Turkish uppercases 'i' to 'İ' rather than 'I', and German 'ß' becomes 'SS' — one character becoming two. Always use your language's locale-aware conversion function.