Convert case

No. Everything happens inside this page, on your own device — nothing is uploaded and no request is made. You can disconnect from the internet after the page loads and it keeps working.

It follows the actual style rule rather than just capitalising every word. "the lord of the rings" becomes "The Lord of the Rings" — "of" and the second "the" stay lowercase, because articles, conjunctions and short prepositions do. The first and last word are always capitalised however minor they are, so "of mice and men" becomes "Of Mice and Men". Most online converters produce "The Lord Of The Rings", which no style guide anywhere endorses.

Because a word with a capital letter inside it was spelled that way deliberately. Re-casing "iPhone" to "Iphone" or "NASA" to "Nasa" would be wrong, so any word carrying an interior capital is passed through untouched.

Turkish and Azeri have two letter i's: a dotted one and a dotless one. Lowercase "i" capitalises to "İ" (with the dot), and "I" lowercases to "ı" (without). So "istanbul" upper-cased under English rules gives "ISTANBUL", which is not the name of the city — it needs "İSTANBUL". This is a well-known source of real bugs, and it is why a language is offered rather than assumed. Greek and Lithuanian have their own rules too, and both are here.

Yes, in every direction — camelCase, PascalCase, snake_case, CONSTANT_CASE, kebab-case, dot.case and path/case all convert between one another. Acronyms are handled properly, which is the part that usually breaks: "XMLHttpRequest" splits into XML, Http and Request, giving "xml_http_request". A converter that only splits at lowercase-to-uppercase boundaries produces "xmlhttp_request".

Sometimes, and you are warned when it is. German "ß" becomes "SS" in capitals and cannot be turned back automatically — "STRASSE" might have been "Straße" or "Strasse". Greek drops its accents in capitals, which is correct Greek but also one-way.