Case rules that differ by language

Changing case is less obvious than it looks once accents are involved. The text is normalised to NFC first, so a letter typed as e followed by a combining acute is treated as the single letter é and keeps its accent all the way through. Uppercase and lowercase then follow the rules of the language you pick instead of one fixed table.

Turkish has two i letters: dotted i pairs with dotted İ, and dotless ı pairs with plain I. Pick Turkish and istanbul becomes İSTANBUL, while ISTANBUL lowercases to ıstanbul. German ß has no traditional capital, so uppercase gives SS by default. Capital ẞ has been an allowed spelling since 2017, so tick the option if you want STRAẞE instead of STRASSE. Dutch writes ij as one digraph and title case capitalises both letters at the start of a word, so ijsland becomes IJsland.

Title case here capitalises the first letter of every word and lowercases the rest, which is the safest rule across languages. Sentence case lowercases everything, then capitalises the first letter of the text and the first letter after a full stop, a question mark or an exclamation mark. Opening punctuation is skipped rather than capitalised, so the Spanish ¿qué tal? comes back as ¿Qué tal?