Which words stay lowercase in Title Case
English title case keeps short function words down: articles like a and the, coordinating conjunctions like and and but, and short prepositions such as of, in and to. Everything else goes up. The first and last word are always capitalised, whatever they are, which is why What Are You Waiting For keeps its final For in capitals.
Style guides disagree about where to draw the line for prepositions. Chicago keeps every preposition lowercase regardless of length; AP capitalises anything of four letters or more. This tool follows Chicago, so four-letter prepositions like over and with stay down. If you are writing to AP style, raise those by hand after copying.
Hyphenated compounds are treated element by element, so state-of-the-art becomes State-of-the-Art and mother-in-law becomes Mother-in-Law.
Title case or sentence case
Sentence case — only the first word and proper nouns capitalised — has been winning for a decade. It is the house style for Google, Apple and most product interfaces, and it reads faster at small sizes. Title case still holds in book titles, news headlines in US papers, and academic citations.
If you are writing UI labels, buttons or navigation, use sentence case. If you are writing a heading that will sit inside a body of formal prose, check what the rest of the document does and match it.
Rescuing text typed in all caps
A page typed with Caps Lock on cannot be fixed by lowercasing alone — you lose the capital letters that belong at the start of sentences and on names. Run it through sentence case instead: the first letter after every full stop, question mark and line break comes back up.
Proper nouns are the part no tool can restore. Names, brands and place names have to go back by hand, so scan the result before you send it.
The four code conventions
Which one to use is decided by the language, not by preference. JavaScript and Java use camelCase for variables and PascalCase for classes; Python and Ruby use snake_case for variables and functions; CSS classes, URLs and filenames use kebab-case; environment variables and constants use CONSTANT_CASE.
Paste a whole list and each line is converted on its own, so a column of names copied out of a spreadsheet or a database schema comes back in one pass. Acronyms are kept together: HTTPServerError splits into http_server_error, not h_t_t_p_server_error.
Languages where case works differently
Korean, Japanese and Chinese have no upper and lower case at all, so those characters pass through untouched — useful when a line mixes English and CJK.
German is the one to watch. The sharp s, ß, has no traditional capital form, so uppercasing turns it into SS: Straße becomes STRASSE. That is the correct and expected result, and it is what German keyboards and passports do too.